Therapeutic and diagnostic tools for impaired glucose tolerance conditions

ABSTRACT

Disclosed herein are novel genes and methods for the screening of therapeutics useful for treating impaired glucose tolerance conditions, as well as diagnostics and therapeutic compositions for identifying or treating such conditions.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application U.S. Ser. No.09/205,658, filed Dec. 3, 1998 now U.S. Pat. No. 6,861,256, which is acontinuation-in-part of PCT/US98/10080, filed May 15, 1998, which is acontinuation-in-part of U.S. Ser. No. 08/888,534, filed Jul. 7, 1997,now abandoned, and U.S. Ser. No. 08/857,076, filed Aug. 3, 2000, whichis a continued prosecution application of U.S. Ser. No. 08/857,076,filed May 15, 1997, now U.S. Pat. No. 6,225,120.

STATEMENT AS TO FEDERALLY SPONSORED RESEARCH

This invention was made in part with support from the Federal governmentthrough NIH Grant Nos. AG05790 and AG14161. The Government has certainrights in the invention.

BACKGROUND OF THE INVENTION

This invention relates to compositions and methods useful for delayingor ameliorating human diseases associated with glucose intolerance.

Diabetes is a major disease affecting over 16 million individuals in theUnited States alone at an annual cost of over 92 billion dollars. Type Idiabetes or insulin-dependent diabetes (IDDD) is an autoimmune disease.In the IDDM patient, the immune system attacks and destroys theinsulin-producing beta cells in the pancreas. The central role ofinsulin in human metabolism is to aid in the transport of glucose intomuscle cells and fat cells. The body's inability to produce insulinresults in hyperglycemia, ketoacidosis, thirst, and weight loss. Inaddition, diabetics often suffer from chronic atherosclerosis and kidneyand eyesight failure. A patient with IDDM requires daily injections ofinsulin to survive.

The most common form of diabetes is non-insulin dependent diabetes(NIDDM) or Type II diabetes. Type II diabetes is a heterogenous group ofdisorders in which hyperglycemia results from both impaired insulinsecretory response to glucose and decreased insulin effectiveness (i.e.,insulin resistance). Older people who are overweight are at particularrisk for Type II diabetes. Genetic studies have suggested that, Type IIdiabetes is found in families and that the disease may be due tomultiple genetic defects. In addition, the link between obesity and TypeII diabetes is strong. Approximately 80 percent of Type II diabetics areobese. Weight loss and exercise can be effective to keep blood glucoselevels normal, reducing the long-term complications of the disease.

At present there are few reliable methods for presymptomatic diagnosisof a genetic predisposition for diabetes or obesity. The search forgenetic markers linked to diabetes and obesity has proven difficult, andthis is especially true for Type II diabetes.

Treatments for diabetes emphasize control of blood glucose through bloodglucose monitoring. The majority of patients take oral medicationsand/or insulin injections for appropriate control. Treatment of diabetesis generally chronic and lifelong, and treatments are generally notsatisfactory over the long run. In addition, insulin treatment maybecome increasingly ineffective as the disease progresses. While insulinhas been known for decades, and within the past decade, the receptorsfor insulin and aspects of its signaling pathway have been identified,the transcriptional output from these signaling pathways have not beencharacterized. In addition, the molecular basis of the obesity-inducedinsulin resistance is unknown.

SUMMARY OF THE INVENTION

We have discovered that the C. elegans metabolic regulatory genes daf-2and age-1 encode homologues of the mammalian insulin receptor/PI3-kinase signaling pathway proteins, respectively. We have alsodiscovered that the C. elegans PKB kinase and AKT kinase act downstreamof these genes, as their mammalian homologues act downstream of insulinsignaling. These results further endorse the congruence between the C.elegans and mammalian insulin signaling pathways, strongly supportingthe contention that new genes identified in the C. elegans pathway alsoact in mammalian insulin signaling. In addition, we have also found thatthe C. elegans PTEN lipid phosphatase homologue, DAF-18, acts upstreamof AKT in this signaling pathway. Thus, our molecular genetic analysismaps mammalian PTEN action to the insulin signaling pathway.

We have also discovered that the DAF-16 forkhead protein represents themajor transcriptional output of this insulin signaling pathway. Forexample, we have discovered that it is the dysregulation of the DAF-16transcription factor in the absence of insulin signaling that leads tometabolic defects; inactivation of DAF-16 reverses the metabolic defectscaused by lack of insulin signaling in C. elegans. We have found 3 humanDAF-16 orthologues: FKHRL1, FKHR, and AFX. Our molecular geneticanalysis strongly suggests that the activity of these transcriptionfactors is strongly coupled to insulin signaling and that drug-inducedinhibition of one or all of these transcription factors amelioratesdiabetic disease. As discussed in more detail below, we have developedscreening strategies to identify such drugs.

We have also found that the C. elegans daf-7, daf-1, daf-4, daf-8,daf-14, and daf-3 genes encode neuroendocrine/target tissue TGF-β typesignal transduction molecules that genetically interact with the insulinsignaling pathway. Similarly, we have shown that the metabolic defectscaused by lack of neuroendocrine TGF-β signals can be reversed byinactivation of the DAF-3 transcription factor. Finally, we have foundthat another C. elegans gene, daf-18, the homologue of the mammalianPTEN lipid phosphatase gene, also functions in the DAF-2 signalingpathway.

Together, this evidence indicates that the DAF-16, DAF-3, DAF-8, andDAF-14 transcriptional outputs of these converging signaling pathwaysregulate metabolism. In addition, these discoveries also indicate thatinsulin and TGF-β-like signals are integrated in humans to regulatemetabolism, and that the homologues of other DAF proteins are likely tobe defective or down regulated in human diabetic pedigrees as well asobesity induced diabetes. These results therefore indicate that the C.elegans daf genes are excellent candidate genes and proteins for humandisease associated with glucose intolerance, e.g., diabetes, obesity,and atherosclerosis. Our findings indicate that the human homologues ofthese daf genes and proteins mediate insulin signaling in normal peopleand may be defective or mis-regulated in diabetics. Moreover, ourfindings indicate that there are at least two classes of type IIdiabetics: those with defects in the TGF-β signaling genes, and thosewith defects in insulin signaling genes. Below we describe exemplarysequence and functional characteristics of the human homologues of thedaf genes.

The discovery of converging DAF-7 and DAF-2 insulin-like signalingindicates that many cases of obesity-induced and genetically-induceddiabetes (and obesity) may be treated by administration of a human DAF-7polypeptide.

The discovery that defects in the TGF-β signaling pathway can besuppressed by decreases in DAF-3 pathway activity and that defects inthe insulin pathway can be suppressed by decreases in DAF-16 activityhighlight the utility of transcriptional regulatory DAF proteins in drugdevelopment; in particular, drugs that inhibit the activity of theseproteins are useful for reversing the effects of obesity-induced orgenetically-induced defects in DAF-7 TGF-β type or insulin signaling.

In one aspect, the invention features a substantially pure preparationof a DAF-2 polypeptide, which can be derived from an animal (forexample, a mammal, such as a human, or an invertebrate, such as C.elegans). In preferred embodiments, the DAF-2 polypeptide has insulinreceptor (InR) activity, insulin receptor related activity, insulin-likegrowth factor receptor (IGF-1) receptor activity, or a combination ofthese activities.

The invention also features isolated DNA encoding a DAF-2 polypeptide.This isolated DNA can have a nucleotide sequence that includes, forexample, the nucleotide sequence of the daf-2 gene shown in FIG. 2B.This isolated DNA can also, in preferred embodiments, complement a daf-2mutation in C. elegans, an InR mutation in a mouse, or an IGF-1 receptormutation in a mouse.

The isolated DNA encoding a DAF-2 polypeptide can be included in avector, such as a vector that is capable of directing the expression ofthe protein encoded by the DNA in a vector-containing cell. The isolatedDNA in the vector can be operatively linked to a promoter, for example,a promoter selected from the group consisting of daf-2, age-1, daf-16,daf-1, daf-4, daf-3, and akt promoters. The isolated DNA encoding aDAF-2 polypeptide, or a vector including this DNA, can be contained in acell, such as a bacterial, mammalian, or nematode cell.

Also included in the invention is a method of producing a recombinantDAF-2 polypeptide, and a DAF-2 polypeptide produced by this method. Thismethod involves (a) providing a cell transformed with isolated DNA that(i) encodes a DAF-2 polypeptide, and (ii) is positioned for expressionin the cell, under conditions for expressing the isolated DNA, and (b)isolating the recombinant DAF-2 polypeptide.

A substantially pure antibody, such as a monoclonal or polyclonalantibody, that specifically recognizes and binds a DAF-2 polypeptide isalso included in the invention.

The invention also features a method of detecting a gene, or a portionof a gene, that is found in a human cell and has sequence identity tothe daf-2 sequence of FIG. 2B. In this method, isolated DNA encoding aDAF-2 polypeptide, a portion of such DNA greater than about 12 residuesin length, or a degenerate oligonucleotide corresponding to SEQ ID NOS:33, 34, 79, 80, 81, 82, 83, or 84, is contacted with a preparation ofDNA from the human cell under hybridization conditions that providedetection of DNA sequences having about 70% or greater nucleic acidsequence identity to the daf-2 sequence of FIG. 2B. This method can alsoinclude a step of testing the gene, or portion thereof, for the abilityto functionally complement a C. elegans daf-2 mutant.

Another method included in the invention is a method of isolating agene, or a portion of a gene, that is found in a human cell and has atleast 90% nucleic acid sequence identity to a sequence encoding SEQ IDNOS: 33, 34, 79, 80, 81, 82, 83, or 84. This method involves (a)amplifying by PCR the human gene, or portion thereof, usingoligonucleotide primers that (i) are each greater than about 12 residuesin length, and (ii) each have regions of complementarity to opposite DNAstrands in a region of the nucleotide sequence of FIG. 2B, and (b)isolating the human gene, or portion thereof. This method can alsoinclude a step of testing the gene, or portion thereof, for the abilityto functionally complement a C. elegans daf-2 mutant.

In another aspect, the invention features a substantially purepreparation of a DAF-3 polypeptide, which can be derived from an animal(for example, a mammal, such as a human, or an invertebrate, such as C.elegans). In a preferred embodiment, the polypeptide is a SMAD protein.In other preferred embodiments, the polypeptide is capable of bindingand interacting with a nematode DAF-1, DAF-4, DAF-8, DAF-14, or DAF-16polypeptide.

The invention also features isolated DNA encoding a DAF-3 polypeptide.This isolated DNA can have a sequence that includes, for example, thenucleotide sequence of a daf-3 gene shown in FIGS. 11A, 11B, or 11C.This isolated DNA can also, in preferred embodiments, complement a daf-3mutation in C. elegans or complement a daf-3 knockout mouse.

The isolated DNA encoding a DAF-3 polypeptide can be included in avector, such as a vector that is capable of directing the expression ofthe protein encoded by the DNA in a vector-containing cell. The isolatedDNA in the vector can be operatively linked to a promoter, for example,a promoter selected from the group consisting of daf-3, daf-4, daf-16,daf-2, age-1, and akt promoters. The isolated DNA encoding a DAF-3polypeptide, or a vector including this DNA, can be contained in a cell,such as a bacterial, mammalian, or nematode cell.

Also included in the invention is a method of producing a recombinantDAF-3 polypeptide, and a DAF-3 polypeptide produced by this method. Thismethod involves (a) providing a cell transformed with isolated DNA that(i) encodes a DAF-3 polypeptide, and (ii) is positioned for expressionin the cell, under conditions for expressing the isolated DNA, and (b)isolating the recombinant DAF-3 polypeptide.

A substantially pure antibody, such as a monoclonal or polyclonalantibody, that specifically recognizes and binds a DAF-3 polypeptide isalso included in the invention.

The invention also features a method of detecting a gene, or a portionof a gene, that is found in a human cell and has sequence identity toany of the daf-3 sequences of FIGS. 11A, 11B, or 11C. In this method,isolated DNA encoding a DAF-3 polypeptide, a portion of such DNA that isgreater than about 12 residues in length, or a degenerateoligonucleotide corresponding to SEQ ID NOS: 35, 36, or 85, is contactedwith a preparation of DNA from the human cell under hybridizationconditions that provide detection of DNA sequences having about 70% orgreater nucleic acid sequence identity to any of the daf-3 sequences ofFIGS. 11A, 11B, or 11C. This method can also include a step of testingthe gene, or portion thereof, for the ability to functionally complementa C. elegans daf-3 mutant.

Another method included in the invention is a method of isolating agene, or a portion thereof, that is found in a human cell and has atleast 90% nucleic acid sequence identity to a sequence encoding SEQ IDNOS: 35, 36, or 85. This method includes (a) amplifying by PCR the humangene, or portion thereof, using oligonucleotide primers that (i) areeach greater than about 12 residues in length, and (ii) each haveregions of complementarity to opposite DNA strands in a region of any ofthe nucleotide sequences of FIGS. 11A, 11B, or 11C, and (b) isolatingthe human gene, or portion thereof. This method can also include a stepof testing the gene, or portion thereof, for the ability to functionallycomplement a C. elegans daf-3 mutant.

In yet another aspect, the invention features a substantially purepreparation of DAF-16 polypeptide, which can be derived from an animal(for example, a mammal, such as a human, or an invertebrate, such as C.elegans). In a preferred embodiment, the polypeptide is a forkheadtranscription factor that binds DNA. In other preferred embodiments, thepolypeptide is capable of interacting with a polypeptide selected fromthe group consisting of DAF-3, DAF-8, and DAF-14.

The invention also features isolated DNA encoding a DAF-16 polypeptide.This isolated DNA can have a sequence that includes, for example, thesequence of the daf-16 gene shown in FIG. 13A or 13B. This isolated DNAcan also, in preferred embodiments, complement a daf-16 mutation in C.elegans, or complement an FKHR, FKHRL1, or AFX mutation in a mouse.

The isolated DNA encoding a DAF-16 polypeptide can be included in avector, such as a vector that is capable of directing the expression ofthe protein encoded by the DNA in a vector-containing cell. The isolatedDNA in the vector can be operatively linked to a promoter, for example,a promoter selected from the group consisting of daf-2, age-1, daf-16,daf-3, daf-4, and akt promoters. The isolated DNA encoding a DAF-16polypeptide, or a vector containing this DNA, can be contained in acell, such as a bacterial, mammalian, or nematode cell.

Also included in the invention is a method for producing a recombinantDAF-16 polypeptide, and a DAF-16 polypeptide produced by this method.This method involves (a) providing a cell transformed with purified DNAthat (i) encodes a DAF-16 polypeptide, and (ii) is positioned forexpression in the cell, under conditions for expressing the isolatedDNA, and (b) isolating the recombinant DAF-16 polypeptide.

A substantially pure antibody, such as a monoclonal or polyclonalantibody, that specifically recognizes and binds a DAF-16 polypeptide isalso included in the invention.

The invention also features a method of detecting a gene, or a portionof a gene, that is found in a human cell and has sequence identity tothe daf-16 sequence of FIG. 13A or 13B. In this method, isolated DNAencoding a DAF-16 polypeptide, a portion of such DNA that is greaterthan about 12 residues in length, or a degenerate oligonucleotidecorresponding to SEQ ID NO: 54, 55, 56, or 57, is contacted with apreparation of DNA from the human cell under hybridization conditionsthat provide detection of DNA sequences having about 70% or greaternucleic acid sequence identity to the daf-16 sequence of FIGS. 13A or13B. This method can also include a step of testing the gene, or portionof the gene, for the ability to functionally complement a C. elegansdaf-16 mutant.

Another method included in the invention is a method of isolating agene, or a portion of a gene, that is found in a human cell and has atleast 90% nucleic acid sequence identity to a sequence encoding SEQ IDNO: 54, 55, 56, or 57. This method involves (a) amplifying by PCR thehuman gene, or portion thereof, using oligonucleotide primers that (i)are each greater than about 12 residues in length, and (ii) each haveregions of complementarity to opposite DNA strands in a region of thenucleotide sequence of FIGS. 13A or 13B, and (b) isolating the humangene, or portion thereof. This method can also include a step of testingthe gene, or portion thereof, for the ability to functionally complementa C. elegans daf-16 mutant.

In another aspect, the invention features a method of determiningwhether a human gene is involved in an impaired glucose tolerancecondition (for example, a condition involving atherosclerosis) orobesity. This method involves (a) providing a nematode having a mutationin a daf or age gene, and (b) expressing in the nematode the human gene,which is operatively linked to a nematode gene promoter. Complementationof the daf or age mutation in the nematode is indicative of a human genethat is involved in an impaired glucose tolerance condition or obesity.In preferred embodiments, the nematode gene promoter is selected fromthe group consisting of daf-1, daf-3, daf-4, daf-2, age-1, and akt genepromoters. In other preferred embodiments, the daf mutation is selectedfrom the group consisting of daf-2, daf-3, daf-1, daf-4, daf-7, daf-8,daf-11, daf-12, daf-14, and daf-16 mutations. In yet another preferredembodiment, the mutation can also be found in the age-1 gene.

In further aspects, the invention features methods for diagnosing animpaired glucose tolerance condition (for example, Type II diabetes or acondition involving atherosclerosis), or a propensity for such acondition, in a patient. One such method includes analyzing the DNA ofthe patient to determine whether the DNA contains a mutation in a dafgene. Identification of such a mutation indicates that the patient hasan impaired glucose tolerance condition or a propensity for such acondition. The analysis in this method can be carried out, for example,by nucleotide sequencing or RFLP analysis. The analysis can also includeamplifying (for example, by PCR or reverse transcriptase PCR) the gene(for example, a human gene), or a fragment thereof, using primers, andanalyzing the amplified gene, or a fragment thereof, for the presence ofthe mutation. In preferred embodiments, the daf gene analyzed in thismethod is, for example, a daf-1, daf-2, daf-3 daf-4, daf-7, daf-8,daf-11, daf-12, daf-14, daf-16, akt-1, akt-2, pdk-1, or daf-18(PTEN)coding sequence, or the daf gene is FKHR, FKHRL1, or AFX.

Another method for diagnosing an impaired glucose tolerance condition,such as Type II diabetes, or a propensity for such a condition, in apatient, includes analyzing the DNA of the patient to determine whetherthe DNA contains a mutation in an age gene. Identification of such amutation indicates that the patient has an impaired glucose tolerancecondition or a propensity for such a condition. The analysis in thismethod can be carried out, for example, by nucleotide sequencing or RFLPanalysis. The analysis can also include amplifying (for example, by PCRor reverse transcriptase PCR) the gene (for example, a human gene), or afragment thereof, using primers and analyzing the amplified gene, orfragment thereof, for the presence of the mutation. In a preferredembodiment, the age gene is an age-1 coding sequence.

Yet another method for diagnosing an impaired glucose tolerancecondition, such as Type II diabetes or a condition that involvesatherosclerosis, or a propensity for such a condition, in a patient,includes analyzing the DNA of the patient to determine whether the DNAcontains a mutation in an akt gene. Identification of such a mutationindicates that the patient has an impaired glucose tolerance condition(for example, Type II diabetes) or a propensity for such a condition(for example, a pre-diabetic condition). The analysis in this method canbe carried out, for example, by nucleotide sequencing or RFLP analysis.The analysis can also include amplifying (for example, by PCR or reversetranscriptase PCR) the gene (for example, a human gene), or a fragmentthereof, using primers and analyzing the amplified gene, or fragmentthereof, for the presence of the mutation.

The invention also includes kits for use in the diagnosis of an impairedglucose tolerance condition, or a propensity for such a condition, in apatient. One such kit includes a PCR primer complementary to a dafnucleic acid sequence and instructions for diagnosing an impairedglucose tolerance condition or a propensity for such a condition.Another kit includes a PCR primer complementary to an age nucleic acidsequence and instructions for diagnosing an impaired glucose tolerancecondition or a propensity for such a condition. Yet another kit includesa PCR primer complementary to an akt nucleic acid sequence andinstructions for diagnosing an impaired glucose tolerance condition or apropensity for such a condition.

In another aspect, the invention features methods for ameliorating ordelaying the onset of an impaired glucose tolerance condition (forexample, Type II diabetes) in a patient. In one such method atherapeutically effective amount of a DAF polypeptide (for example, thehuman or nematode DAF-7 polypeptide) is administered to the patient. Inanother method, which can be used, for example, in the case of acondition involving atherosclerosis, a therapeutically effective amountof a compound that is capable of inhibiting the activity of a DAF-16 orDAF-3 polypeptide is administered to the patient. In yet another method,a therapeutically effective amount of a compound that activates a DAF-1,DAF-4, DAF-8, DAF-11, or DAF-14 polypeptide is administered to thepatient.

Another aspect of the invention provides methods for ameliorating orpreventing obesity (for example, obesity associated with Type IIdiabetes) in a patient. One such method involves administering to thepatient a therapeutically effective amount of a DAF polypeptide, such asa human or nematode DAF-7 polypeptide. Another such method involvesadministering to the patient a therapeutically effective amount of acompound that is capable of inhibiting the activity of a DAF-16, DAF-3,or DAF-18 (PTEN) polypeptide.

Yet another aspect of the invention features a transgenic, non-humananimal, such as a mouse or a nematode, whose germ cells and somaticcells contain a transgene coding for a mutant DAF polypeptide, forexample, a mutant DAF polypeptide that is derived from a human. Inpreferred embodiments, the mutant DAF polypeptide is a DAF-1, DAF-2,DAF-3, DAF-4, DAF-7, DAF-8, DAF-11, DAF-12, DAF-14, DAF-16, or DAF-18(PTEN) polypeptide. In another preferred embodiment, the transgeneincludes a knockout mutation.

In a related aspect, the invention features a transgenic, non-humananimal, such as a mouse or a nematode, whose germ cells and somaticcells contain a transgene coding for a mutant AGE polypeptide, forexample, a mutant AGE polypeptide derived from a human. In a preferredembodiment, the mutant AGE polypeptide is an AGE-1 polypeptide. Inanother preferred embodiment, the transgene includes a knockoutmutation.

In yet another aspect, the invention features a transgenic, non-humananimal, such as a mouse or a nematode, whose germ cells and somaticcells contain a transgene coding for a mutant AKT polypeptide, forexample, a mutant AKT polypeptide derived from a human. In a preferredembodiment, the transgene includes a knockout mutation.

In related aspects, the invention features cells (for example, cellsisolated from a mammal, such as mouse, human, or nematode cells)isolated from the transgenic animals described above.

The invention also includes methods for producing transgenic, non-humananimals. For example, the invention includes a method for producing atransgenic, non-human animal that lacks an endogenous daf gene and iscapable of expressing a human DAF polypeptide. This method involves (a)providing a transgenic, non-human animal whose germ cells and somaticcells contain a mutation in a daf gene, and (b) introducing a transgenethat (i) encodes a human DAF polypeptide, and (ii) is capable ofexpressing the human polypeptide, into an embryonal cell of thenon-human animal.

Another method included in the invention can be used for producing atransgenic, non-human animal that lacks an endogenous age gene and iscapable of expressing a human AGE polypeptide. This method involves (a)providing a transgenic, non-human animal whose germ cells and somaticcells contain a mutation in an age gene, and (b) introducing a transgenethat (i) encodes a human AGE polypeptide, and (ii) is capable ofexpressing the human polypeptide, into an embryonal cell of thenon-human animal.

Similarly, the invention includes a method for producing a transgenic,non-human animal that lacks an endogenous akt gene and is capable ofexpressing of expressing a human AKT polypeptide. This method involves(a) providing a transgenic, non-human animal whose germ cells andsomatic cells contain a mutation in an akt gene, and (b) introducing atransgene that (i) encodes a human AKT polypeptide, and (ii) is capableof expressing the human polypeptide, into an embryonal cell of thenon-human animal.

Another aspect of the invention features a method of screening for acompound that increases the activity of a DAF polypeptide. This methodincludes (a) exposing a non-human transgenic animal whose germ cells andsomatic cells contain a transgene coding for a mutant DAF polypeptide toa candidate compound, and (b) determining the activity of the DAFpolypeptide in the transgenic animal. An increase in DAF polypeptideactivity, as compared to untreated controls, is indicative of a compoundthat is capable of increasing DAF polypeptide activity. In preferredembodiments, the compound can be used to treat an impaired glucosetolerance condition or obesity.

In a related aspect, the invention features a method of screening for acompound that decreases the activity of a DAF polypeptide. This methodincludes (a) exposing a non-human transgenic animal whose germ cells andsomatic cells contain a transgene coding for a mutant DAF polypeptide toa candidate compound, and (b) determining the activity of the DAFpolypeptide in the transgenic animal. A decrease in DAF polypeptideactivity, as compared to untreated controls, is indicative of a compoundthat is capable of decreasing DAF polypeptide activity. In preferredembodiments, the compound can be used to treat an impaired glucosetolerance condition, obesity, or atherosclerosis. In other preferredembodiments, the compound decreases the activity of DAF-3 or DAF-16.

In another aspect, the invention features a method of screening for acompound that increases the activity of an AGE polypeptide. This methodincludes (a) exposing a non-human transgenic animal whose germ cells andsomatic cells contain a transgene coding for a mutant AGE polypeptide toa candidate compound, and (b) determining the activity of the AGEpolypeptide in the transgenic animal. An increase in AGE polypeptideactivity, as compared to untreated controls, is indicative of a compoundthat is capable of increasing AGE polypeptide activity. In preferredembodiments, the compound can be used to treat an impaired glucosetolerance condition, obesity, or atherosclerosis.

In a related aspect, the invention features a method of screening for acompound that decreases the activity of a AGE polypeptide. This methodincludes (a) exposing a non-human, transgenic animal whose germ cellsand somatic cells contain a transgene coding for a mutant AGEpolypeptide to a candidate compound, and (b) determining the activity ofthe AGE polypeptide in the transgenic animal. A decrease in AGEpolypeptide activity, as compared to untreated controls, is indicativeof a compound that is capable of decreasing AGE polypeptide activity. Inpreferred embodiments, the compound can be used to treat or delay aging.In another preferred embodiment, the AGE polypeptide is AGE-1.

In another aspect, the invention features a method of screening for acompound that increases the activity of an AKT polypeptide. This methodincludes (a) exposing a transgenic, non-human animal whose germ cellsand somatic cells contain a transgene coding for a mutant AKTpolypeptide to a candidate compound, and (b) determining the activity ofthe AKT polypeptide in the transgenic animal. An increase in AKTpolypeptide activity, as compared to untreated controls, is indicativeof a compound that is capable of increasing AKT polypeptide activity. Inpreferred embodiments, the compound can be used to treat an impairedglucose tolerance condition, obesity, or atherosclerosis.

In a related aspect, the invention features a method of screening for acompound that decreases the activity of a AKT polypeptide. This methodincludes (a) exposing a transgenic, non-human animal whose germ cellsand somatic cells contain a transgene coding for a mutant AKTpolypeptide to a candidate compound, and (b) determining the activity ofthe AKT polypeptide in the transgenic animal. A decrease in AKTpolypeptide activity, as compared to untreated controls, is indicativeof a compound that is capable of decreasing AKT polypeptide activity. Inpreferred embodiments, the compound can be used to treat or delay aging.

Also included in the invention is a method of screening for a compoundthat is capable of ameliorating or delaying an impaired glucosetolerance condition. This method involves (a) exposing a transgenic,non-human animal whose germ cells and somatic cells contain a transgenecoding for a mutant DAF, AGE, or AKT polypeptide to a candidatecompound, and (b) monitoring the blood glucose level of the animal. Acompound that promotes maintenance of a physiologically acceptable levelof blood glucose in the animal, as compared to untreated controls, isindicative of a compound that is capable of ameliorating or delaying animpaired glucose tolerance condition. In a preferred embodiment, thecompound can be used to treat Type II diabetes.

Another method of screening for a compound that is capable ofameliorating or delaying obesity is also included in the invention. Thismethod involves (a) exposing a transgenic, non-human animal whose germcells and somatic cells contain a transgene coding for a mutant DAF,AGE, or AKT polypeptide to a candidate compound, and (b) monitoring theadipose tissue of the animal. A compound that promotes maintenance of aphysiologically acceptable level of adipose tissue in the animal, ascompared to untreated controls, is indicative of a compound that iscapable of ameliorating or delaying obesity.

A related method of the invention can be used for screening for acompound that is capable of ameliorating or delaying atherosclerosis.This method involves (a) exposing a transgenic, non-human animal whosegerm cells and somatic cells contain a transgene coding for a mutantDAF, AGE, or AKT polypeptide to a candidate compound, and (b) monitoringthe adipose tissue of the animal. A compound that promotes maintenanceof a physiologically acceptable level of adipose tissue in the animal,as compared to untreated controls, is indicative of a compound that iscapable of ameliorating or delaying atherosclerosis.

In another aspect, the invention includes a method for identifying amodulatory compound that is capable of decreasing the expression of adaf gene. This method involves (a) providing a cell expressing the dafgene, and (b) contacting the cell with a candidate compound. A decreasein daf expression following contact with the candidate compoundidentifies a modulatory compound. In preferred embodiments, the compoundcan be used to treat an impaired glucose tolerance condition or obesity.In other preferred embodiments, the compound is capable of decreasingthe expression of DAF-3 or DAF-16. This method can be carried out in ananimal, such as a nematode.

In a related aspect, the invention includes a method for theidentification of a modulatory compound that is capable of increasingthe expression of a daf gene. This method involves (a) providing a cellexpressing the daf gene, and (b) contacting the cell with a candidatecompound. An increase in daf expression following contact with thecandidate compound identifies a modulatory compound. In preferredembodiments, the compound can be used to treat an impaired glucosetolerance condition or obesity. In other preferred embodiments, thecompound is capable of increasing expression of DAF-1, DAF-2, DAF-4,DAF-7, DAF-8, DAF-11, or DAF-14. This method can be carried out in ananimal, such as a nematode.

In another aspect, the invention includes a method for theidentification of a modulatory compound that is capable of increasingthe expression of an age-1 gene. This method involves (a) providing acell expressing the age-1 gene, and (b) contacting the cell with acandidate compound. An increase in age-1 expression following contactwith the candidate compound identifies a modulatory compound. Inpreferred embodiments, the compound is capable of treating an impairedglucose tolerance condition or obesity. This method can be carried outin an animal, such as a nematode.

In another aspect, the invention provides a method for identification ofa compound that is capable of ameliorating or delaying an impairedglucose tolerance condition. This method involves (a) providing a dauerlarvae including a mutation in a daf gene, and (b) contacting the dauerlarvae with a compound. Release from the dauer larval state is anindication that the compound is capable of ameliorating or delaying animpaired glucose tolerance condition. In a preferred embodiment, thedauer larvae carries a daf-2 mutation. In another preferred embodiment,the dauer larvae is from C. elegans. In yet another embodiment, theimpaired glucose tolerance condition involves obesity oratherosclerosis.

In a related aspect, the invention provides a method for identificationof a compound that is capable of ameliorating or delaying an impairedglucose tolerance condition. This method involves (a) providing a dauerlarvae including a mutation in an age-1 gene, and (b) contacting thedauer larvae with a compound. Release from the dauer larval state is anindication that the compound is capable of ameliorating or delaying animpaired glucose tolerance condition. In a preferred embodiment, thedauer larvae carries an age-1 mutation. In another preferred embodiment,the dauer larvae is from C. elegans. In yet another preferredembodiment, the impaired glucose tolerance condition involves obesity oratherosclerosis.

In another related aspect, the invention provides a method for theidentification of a compound that is capable of ameliorating or delayingan impaired glucose tolerance condition. This method involves (a)providing a dauer larvae including a mutation in an akt gene, and (b)contacting the dauer larvae with a compound. Release from the dauerlarval state is an indication that the compound is capable ofameliorating or delaying an impaired glucose tolerance condition. In apreferred embodiment, the dauer larvae is from C. elegans. In anotherpreferred embodiment, the impaired glucose tolerance condition involvesobesity or atherosclerosis.

In another aspect, the invention provides a method for theidentification of a compound for ameliorating or delaying an impairedglucose tolerance condition. This method involves (a) combining PIP3 andan AKT polypeptide in the presence and absence of a compound underconditions that allow PIP3 :AKT complex formation, (b) identifying acompound that is capable of decreasing the formation of the PIP3:AKTcomplex, and (c) determining whether the compound identified in step (b)is capable of increasing AKT activity. An increase in AKT kinaseactivity is taken as an indication of a compound useful for amelioratingor delaying an impaired glucose tolerance condition.

In yet another aspect, the invention provides a method for theidentification of a compound for ameliorating or delaying an impairedglucose tolerance condition. This method involves (a) providing a daf-7,daf-3 mutant nematode, (b) expressing in the cells of the nematode amammalian DAF-3 polypeptide, whereby the nematode forms a dauer larva,and (c) contacting the dauer larva with a compound. A release from thedauer larval state is an indication that the compound is capable ofameliorating or delaying the glucose intolerance condition.

In a further aspect, the invention features a method for theidentification of a compound for ameliorating or delaying an impairedglucose tolerance condition. This method involves (a) providing a daf-2,daf-16 mutant nematode, (b) expressing in the cells of the nematode amammalian DAF-16 polypeptide, whereby the nematode forms a dauer larva,and (c) contacting the dauer larva with a compound. A release from thedauer larval state is an indication that the compound is capable ofameliorating or delaying the glucose intolerance condition.

In yet another aspect, the invention features insulin-like molecules andtheir use as diagnostic and therapeutic reagents.

As used herein, by a “DAF” polypeptide is meant a polypeptide thatfunctionally complements a C. elegans daf mutation and/or that has atleast 60%, preferably 75%, and more preferably 90% amino acid sequenceidentity to a 100 amino acid region (and preferably a conserved domain)of a C. elegans DAF polypeptide. Complementation may be assayed in anorganism (for example, in a nematode) or in a cell culture system.Complementation may be partial or complete, but must provide adetectable increase in function (as described herein). DAF polypeptidesare encoded by “DAF” genes or nucleic acid sequences.

By an “AGE” polypeptide is meant a polypeptide that functionallycomplements a C. elegans age mutation and/or that has at least 60%,preferably 75%, and more preferably 90% amino acid sequence identity toa 100 amino acid region (and preferably a conserved domain) of a C.elegans AGE polypeptide. Complementation may be assayed in an organism(for example, in a nematode) or in a cell culture system.Complementation may be partial or complete, but must provide adetectable increase in a known AGE function. AGE polypeptides areencoded by “AGE” genes or nucleic acid sequences.

As used herein, by an “AKT” polypeptide is meant a polypeptide thatfunctionally complements a C. elegans akt mutation and/or that possessat least 64% amino acid sequence identity to SEQ ID NO: 60, at least 71%amino acid sequence identity to SEQ ID NO: 61, at least 79% amino acidsequence identity to SEQ ID NO: 62, at least 63% amino acid sequenceidentity to SEQ ID NO: 63, at least 48% amino acid sequence identity toSEQ ID NO: 64, at least 70% amino acid sequence identity to SEQ ID NO:65, at least 64% amino acid sequence identity to SEQ ID NO: 66, at least67% amino acid sequence identity to SEQ ID NO: 67, or a combinationthereof. Complementation may be assayed in an organism (for example, ina nematode) or in a cell culture system. Complementation may be partialor complete, but must provide a detectable increase in a known AKTfunction. AKT polypeptides are encoded by “AKT” genes or nucleic acidsequences.

By a “DAF-2 polypeptide” is meant a polypeptide that complements (asdefined above) a C. elegans daf-2 mutation and/or that possesses atleast 61% amino acid sequence identity to SEQ ID NO: 33, at least 31%amino acid sequence identity to SEQ ID NO: 34, at least 43% amino acidsequence identity to SEQ ID NO: 79, at least 35% amino acid sequenceidentity to SEQ ID NO: 80, at least 35% amino acid sequence identity toSEQ ID NO: 81, at least 48% amino acid sequence identity to SEQ ID NO:82, at least 43% amino acid sequence identity to SEQ ID NO: 83, at least40% amino acid sequence identity to SEQ ID NO: 84, or a combinationthereof. Preferably, a DAF-2 polypeptide includes an aspartic acid, aproline, a proline, a serine, an alanine, an aspartic acid, a cysteine,or a proline at amino acid positions corresponding to C. elegans DAF-2amino acids 1252, 1312, 1343, 347, 451, 458, 526, 279, and 348respectively, or a combination thereof.

By a “DAF-3 polypeptide” is meant a polypeptide that complements (asdefined above) a C. elegans daf-3 mutation and/or that possesses atleast 60% amino acid sequence identity to SEQ ID NO: 35, at least 38%amino acid sequence identity to SEQ ID NO: 36, at least 47% amino acidsequence identity to SEQ ID NO: 85, or a combination thereof.Preferably, a DAF-3 polypeptide includes a proline or a glycine at aminoacid positions corresponding to C. elegans daf-3 amino acids atpositions 200 (proline) and/or 620 (glycine) in FIG. 12A, respectively,or a combination thereof. For example, the polypeptide may include aproline in the motif GRKGFPHV (SEQ ID NO:322) or a glycine in the motifRXXIXXG (where X is any amino acid)(SEQ ID NO:323).

By a “DAF-16 polypeptide” is meant a polypeptide that complements (asdefined above) a C. elegans daf-16 mutation and/or that possesses atleast 71% amino acid sequence identity to SEQ ID NO: 54, at least 35%amino acid sequence identity to SEQ ID NO: 55, at least 65% amino acidsequence identity to SEQ ID NO: 56, at least 53% amino acid sequenceidentity to SEQ ID NO: 57, or a combination thereof. In addition, aDAF-16 polypeptide preferably includes a serine residue in the conservedmotif WKNSIRH (SEQ ID NO: 59).

By a “DAF-7 polypeptide” is meant a polypeptide that complements (asdefined above) a C. elegans daf-7 mutation and/or that possesses atleast 29% amino acid sequence identity to SEQ ID NO: 26, at least 66%amino acid sequence identity to SEQ ID NO: 27, at least 45% amino acidsequence identity to SEQ ID NO: 28, at least 33% amino acid sequenceidentity to SEQ ID NO: 29, at least 56% amino acid sequence identity toSEQ ID NO: 30, at least 75% sequence identity to SEQ ID No: 51, or acombination thereof. Preferably, a DAF-7 polypeptide includes a prolineor a glycine at amino acid positions corresponding to C. elegans daf-7amino acids 271 and 280, respectively, or a combination thereof.

By a “DAF-8 polypeptide” is meant a polypeptide that complements (asdefined above) a C. elegans daf-8 mutation and/or that possesses atleast 46% amino acid sequence identity to SEQ ID NO: 23, at least 45%amino acid sequence identity to SEQ ID NO: 24, at least 36% amino acidsequence identity to SEQ ID NO: 25, or a combination thereof.

By an “AGE-1 polypeptide” is meant a polypeptide that complements (asdefined above) a C. elegans age-1 mutation (previously known as a daf-23mutation) and/or that possesses at least 40% amino acid sequenceidentity to SEQ ID NO: 17, at least 45% amino acid sequence identity toSEQ ID NO: 18, at least 30% amino acid sequence identity to SEQ ID NO:19, at least 24% amino acid sequence identity to SEQ ID NO: 38, or acombination thereof. Preferably, an AGE-1 polypeptide includes analanine at amino acid positions corresponding to C. elegans age-1 aminoacids 845.

By a “DAF-1 polypeptide” is meant a polypeptide that complements (asdefined above) a C. elegans daf-1 mutation and/or that possesses atleast 45% amino acid sequence identity to SEQ ID NO: 13, at least 35%amino acid sequence identity to SEQ ID NO: 14, at least 65% amino acidsequence identity to SEQ ID NO: 15, at least 25% amino acid sequenceidentity to SEQ ID NO: 16, or a combination thereof. Preferably, a DAF-1polypeptide includes a proline at the amino acid position correspondingto C. elegans DAF-1 amino acid 546.

By a “DAF-4 polypeptide” is meant a polypeptide that complements (asdefined above) a C. elegans daf-4 mutation and/or that possesses atleast 45% amino acid sequence identity to SEQ ID NO: 20, at least 40%amino acid sequence identity to SEQ ID NO: 21, at least 44% amino acidsequence identity to SEQ ID NO: 22, or a combination thereof.

By a “DAF-11 polypeptide” is meant a polypeptide that complements (asdefined above) a C. elegans daf-11 mutation and/or that possesses atleast 40% amino acid sequence identity to SEQ ID NO: 75, at least 43%amino acid sequence identity to SEQ ID NO: 76, at least 36% amino acidsequence identity to SEQ ID NO: 77, at least 65% amino acid sequenceidentity to SEQ ID NO: 78, or a combination thereof.

By a “DAF-12 polypeptide” is meant a polypeptide that complements (asdefined above) a C. elegans daf-12 mutation and/or that possesses atleast 42% amino acid sequence identity to SEQ ID NO: 72, at least 58%amino acid sequence identity to SEQ ID NO: 73, at least 34% amino acidsequence identity to SEQ ID NO: 74, or a combination thereof.

By a “DAF-14 polypeptide” is meant a polypeptide that complements (asdefined above) a C. elegans daf-14 mutation and/or that possesses atleast 48% amino acid sequence identity to SEQ ID NO: 68, at least 37%amino acid sequence identity to SEQ ID NO: 69, at least 48% amino acidsequence identity to SEQ ID NO: 70, at least 37% amino acid sequenceidentity to SEQ ID NO: 71, or a combination thereof.

By a “PTEN” polypeptide is meant a PTEN lipid phosphatase from anyanimal. Preferably, this animal is a mammal and, most preferably, ahuman. This polypeptide is also referred to as MMAC1 and TEP1.

By “insulin receptor activity” is meant any activity exhibited by aninsulin receptor and measured by either (i) activation of insulinreceptor substrate-1 (IRS-1) phosphorylation and recruitment of PI-3kinase, (ii) activation of glucose transporter (Glut 4) fusion with acellular membrane and concomitant glucose uptake, or (iii) activation ofglycogen and/or fat synthesis and concomitant inhibition ofgluconeogenesis or lipolysis or both.

By “insulin receptor related activity” is meant any activity notdirectly attributable to the insulin receptor but that is measured by anactivation of IRS-1 phosphorylation and recruitment of PI3-kinase.

By “IGF-1 receptor activity” is meant any activity exhibited by aninsulin-like growth factor-1 receptor and measured by (i) activation ofIRS-1 phosphorylation and recruitment of PI-3 kinase, (ii) activation ofcell division in NIH3T3 cells (e.g., as described in Gronborg et al., J.Biol. Chem. 268: 23435–23440, 1993), or (iii) activation of bone growthin, for example, the mouse model.

By “SMAD protein” is meant a protein that is capable of coupling toTGF-β type ser/thr receptors. Smad proteins typically contain a smadconserved motif as described by Derynk et al. (Cell 87: 173, 1996).Exemplary smad proteins include, without limitation, DAF-3, MADR-2, MAD,DPC-4, and Sma-2.

By “AKT activity” is meant any activity exhibited by an AKT polypeptideand measured by phosphatidylinositol-regulated increases in serinephosphorylation of GSK-3, DAF-16, AFX, FKHR, or FKHRL1, or activation ofnon-dauer growth in C. elegans akt mutants.

By “impaired glucose tolerance condition” is meant any condition inwhich blood sugar levels are inappropriately elevated or lack normalmetabolic regulation. Examples of such conditions include, withoutlimitation, Type I diabetes, Type II diabetes, and gestational diabetes,and may be associated with obesity and atherosclerosis.

By “protein” or “polypeptide” is meant any chain of amino acids,regardless of length or post-translational modification (e.g.,glycosylation or phosphorylation).

By “substantially pure” is meant a preparation which is at least 60% byweight (dry weight) the compound of interest, e.g., any of thepolypeptides of the invention such as the DAF-2, DAF-3, or DAF-16polypeptides or DAF-2, DAF-3, or DAF-16-specific antibodies. Preferablythe preparation is at least 75%, more preferably at least 90%, and mostpreferably at least 99%, by weight the compound of interest. Purity canbe measured by any appropriate method, e.g., column chromatography,polyacrylamide gel electrophoresis, or HPLC analysis.

By “isolated DNA” is meant DNA that is not immediately contiguous withboth of the coding sequences with which it is immediately contiguous(one on the 5′ end and one on the 3′ end) in the naturally-occurringgenome of the organism from which it is derived. The term thereforeincludes, for example, a recombinant DNA which is incorporated into avector; into an autonomously replicating plasmid or virus; or into thegenomic DNA of a prokaryote or eukaryote, or which exists as a separatemolecule (e.g., a cDNA or a genomic DNA fragment produced by PCR orrestriction endonuclease treatment) independent of other sequences. Italso includes a recombinant DNA which is part of a hybrid gene encodingadditional polypeptide sequence.

By a “substantially identical” polypeptide sequence is meant an aminoacid sequence which differs only by conservative amino acidsubstitutions, for example, substitution of one amino acid for anotherof the same class (e.g., valine for glycine, arginine for lysine, etc.)or by one or more non-conservative substitutions, deletions, orinsertions located at positions of the amino acid sequence which do notdestroy the function of the polypeptide (assayed, e.g., as describedherein).

Preferably, such a sequence is at least 75%, more preferably 85%, andmost preferably 95% identical at the amino acid level to the sequenceused for comparison.

Homology is typically measured using sequence analysis software (e.g.,Sequence Analysis Software Package of the Genetics Computer Group,University of Wisconsin Biotechnology Center, 1710 University Avenue,Madison, Wis. 53705 or BLAST software available from the NationalLibrary of Medicine). Examples of useful software include the programs,Pileup and PrettyBox. Such software matches similar sequences byassigning degrees of homology to various substitutions, deletions,substitutions, and other modifications. Conservative substitutionstypically include substitutions within the following groups: glycine,alanine; valine, isoleucine, leucine; aspartic acid, glutamic acid,asparagine, glutamine; serine, threonine; lysine, arginine; andphenylalanine, tyrosine.

By a “substantially identical” nucleic acid is meant a nucleic acidsequence which encodes a polypeptide differing only by conservativeamino acid substitutions, for example, substitution of one amino acidfor another of the same class (e.g., valine for glycine, arginine forlysine, etc.) or by one or more non-conservative substitutions,deletions, or insertions located at positions of the amino acid sequencewhich do not destroy the function of the polypeptide (assayed, e.g., asdescribed herein). Preferably, the encoded sequence is at least 75%,more preferably 85%, and most preferably 95% identical at the amino acidlevel to the sequence of comparison. If nucleic acid sequences arecompared a “substantially identical” nucleic acid sequence is one whichis at least 85%, more preferably 90%, and most preferably 95% identicalto the sequence of comparison. The length of nucleic acid sequencecomparison will generally be at least 50 nucleotides, preferably atleast 60 nucleotides, more preferably at least 75 nucleotides, and mostpreferably 110 nucleotides. Again, homology is typically measured usingsequence analysis software (e.g., Sequence Analysis Software Package ofthe Genetics Computer Group, University of Wisconsin BiotechnologyCenter, 1710 University Avenue, Madison, Wis. 53705).

By “positioned for expression” is meant that the DNA molecule ispositioned adjacent to a DNA sequence which directs transcription andtranslation of the sequence (i.e., facilitates the production of any ofthe polypeptides disclosed herein including, but not limited to, DAF-2,DAF-3, and DAF-16 and any human homolog thereof).

By “purified antibody” is meant antibody which is at least 60%, byweight, free from the proteins and naturally-occurring organic moleculeswith which it is naturally associated. Preferably, the preparation is atleast 75%, more preferably at least 90%, and most preferably at least99%, by weight, antibody.

By “specifically binds” is meant an antibody which recognizes and bindsa polypeptide of the invention (e.g., DAF-2, DAF-3, and DAF-16) butwhich does not substantially recognize and bind other molecules in asample (e.g., a biological sample) which naturally includes apolypeptide of the invention. An antibody which “specifically binds”such a polypeptide is sufficient to detect protein product in such abiological sample using one or more of the standard immunologicaltechniques available to those in the art (for example, Western blottingor immunoprecipitation).

By “immunological methods” is meant any assay involving antibody-baseddetection techniques including, without limitation, Western blotting,immunoprecipitation, and direct and competitive ELISA and RIAtechniques.

By “means for detecting” is meant any one or a series of components thatsufficiently indicate a detection event of interest. Such means involveat least one label that may be assayed or observed, including, withoutlimitation, radioactive, fluorescent, and chemiluminescent labels.

By “hybridization techniques” is meant any detection assay involvingspecific interactions (based on complementarity) between nucleic acidstrands, including DNA-DNA, RNA-RNA, and DNA-RNA interactions. Suchhybridization techniques may, if desired, include a PCR amplificationstep.

By a “modulatory compound”, as used herein, is meant any compoundcapable of either decreasing DAF-3, DAF-16, or DAF-18 (PTEN) expression(i.e., at the level of transcription, translation, or post-translation)or decreasing DAF-3, DAF-16, or DAF-18 (PTEN) protein levels oractivity. Also included are compounds capable of either increasingDAF-1, DAF-2, DAF-4, DAF-8, DAF-7, DAF-11, DAF-14, AGE-1, AKT, or PDK1expression (i.e., at the level of transcription, translation, orpost-translation) or increasing DAF-1, DAF-2, DAF-4, DAF-8, DAF-7,DAF-11, DAF-14, AGE-1, AKT, or PDK-1 protein levels or theircorresponding activities.

By “complementation” is meant an improvement of a genetic defect ormutation. In one example, complementation of a genetic defect in a daf,age, or akt gene can be carried out by providing the wild-type daf, age,or akt genes, respectively. Complementation is generally accomplished byexpressing the wild-type version of the protein in a host cell or animalbearing a mutant or inactive version of the gene.

Other features and advantages of the invention will be apparent from thefollowing detailed description thereof, and from the claims.

DETAILED DESCRIPTION

The drawings will first be described.

DRAWINGS

FIG. 1 shows the genetic and physical map of C. elegans daf-2. The toppanel shows the genetic map of daf-2. daf-2 maps on the left arm ofchromosome III 11.4 map units to the right of dpy-1 and 1.6 map units tothe left of ben-1 (ACeDB). The middle panel shows the physical map ofdaf-2. daf-2 maps between mgP34 and mgP44 in a region not covered bycosmid clones but covered by YAC Y53G8. Cosmids from the approximatedaf-2 genetic location detect RFLPs between C. elegans strains BristolN2 and Bergerac RC301. mgP31 on cosmid T21A6 is a HindIII RFLP: 5.3 kbin Bristol, 4.5 kb in RC301. mgP33 on cosmid T02B2 is a HindIII RFLP: 9kb in Bristol, 8 kb in RC301. mgP34 on cosmid R10F2 is an EcoRI RFLP:4.1 and 2.8 kb in Bristol, 3.6 kb in RC301. mgP44 on cosmid R07G11 is acomplex EcoRI RFLP: 2.9 kb, 2.4 kb, 1.9 kb and 1.7 kb in Bristol; 3.6kb, 2.5 kb and 1.6 kb in RC301. mgP35 on cosmid T10D5 is a StyI RFLP:5.4 kb in Bristol, 5.8 kb in RC301. mgP32 on cosmid C42B8 is a StyIRFLP: 2.8 kb in Bristol; 2.9 kb in RC301. mgP48 detected with daf-2probe (nt 1277-2126 and 3747-4650) is a HindIII RFLP: 4.3 kb and 7 kb inBristol and 4.1 kb and 6.2 kb in RC301. Thirty-one out of thirty-threeDpy-non-Daf recombinants carry the RC301 allele of mgP34 whereas allthirty-three recombinants in this interval carry the RC301 allele ofmgP44, mapping daf-2 0.69 map units to the right of mgP34 and to theleft of mgP44. Fourteen out of twenty-four Ben-non-Daf recombinantscarry the RC301 mgP44 allele whereas all of these recombinants carry theRC301 allele of mgP34, mapping daf-2 0.66 map units to the left ofmgP44.

Y53G8 YAC DNA was isolated from CHEF gels as described in Ausubel et al.(Current Protocols in Molecular Biology, John Wiley & Sons, New York,N.Y., 1990), labeled, and shown to hybridize to multiple restrictionfragments from cosmids bearing mgP34 and mgP44. A probe from the insulinreceptor homolog on Y53G8 detects the mgP48 RFLP between N2 and RC301.All thirty-three Dpy-non-Daf and all twenty-four Ben-non-Dafrecombinants described above carry the RC301 allele of mgP48, indicatingthat daf-2 could not be separated from this insulin receptor gene bythese fifty-seven recombination events in a thirteen map unit interval.

The bottom panel shows the structure of daf-2 cDNA. The daf-2 cDNA wasamplified from a cDNA library constructed according to standard methodsby PCR using internal primers derived from the genomic shotgunsequences, vector sequence primers (for 3′ end) and an SL1 transsplicedleader PCR primer (M. Krause, In: Methods Cell Biol., vol. 48, pp.483–512, H. F. Epstein and D. C. Shakes, eds., Academic Press, SanDiego, Calif., 1995). To isolate a cDNA, pooled plasmid DNA from 106clones of a 107 clone complexity cDNA library was used as a PCRtemplate. To obtain a daf-2 cDNA 3′ end, daf-2 internal primerCGCTACGGCAAAAAAGTGAA (SEQ ID NO: 1) in the kinase domain and a cloningvector primer CGATGATGAAGATACCCC (SEQ ID NO: 2) were used in a nestedPCR reaction with adjacent internal primers. For the cDNA fragment fromthe ligand-binding domain to the kinase domain, PCR was carried out withTGATGCGAACGGCGATCGAT (SEQ ID NO: 3) and ACGCTGGATCATCTACATTA (SEQ ID NO:4) primers. For the daf-2 5′ end, SL1 primer GGTTTAATTACCCAAGTTTGAG (SEQID NO: 5) and one internal daf-2 primer GCTCACGGGTCACACAACGA (SEQ ID NO:6) were used in a nested PCR reaction with adjacent internal primers.Using PCR to amplify genomic DNA from a set of 20 daf-2 mutants, wesearched for daf-2 mutations in a 0.8 kb region of the ligand bindingdomain and in a 0.9 kb region of the kinase domain. For sequencing theligand-binding domain PCR primers TGATGCGAACGGCGATCGAT (SEQ ID NO: 7)and TGAGGGCCAACTAAAGAAGAC (SEQ ID NO: 8) were used. In the kinase domainprimers CGCTACGGCAAAAAAGTGAA (SEQ ID NO: 9) and GACGATCCCGAGGTGAGTAT(SEQ ID NO: 10) were used. The presence of an SL1 spliced leadersequence indicates a full length daf-2 cDNA. The predicted ORF is shownas a box; 5′ and 3′ UTRs are shown as thick bars. The predicted DAF-2initiator methionine at base 486 is preceded by an in frame stop codon63 bases upstream. The predicted DAF-2 stop codon is found at base 5658.No consensus polyadenylation signal was found in the cDNA nor in genomicshotgun sequence #00678, which extends 302 bp further downstream. Theinitial insulin receptor homolog shotgun sequences are shown as thinbars above the box.

Introns were detected by a combination of in silico genomic and cDNAsequence comparison, and by comparison of PCR products derived from cDNAand genomic DNA templates. The open triangles over a vertical barindicate positions of the detected exon/intron boundaries. All theintron donor sites have GT consensus and the acceptor sites have AGconsensus (Krause, 1995 supra). The triangles without a vertical barindicate the approximate intron locations determined by comparison ofPCR products using genomic DNA or cDNA as a template. Intron lengthswere estimated by comparison of the PCR product size using cDNA orgenomic DNA templates. Genomic regions corresponding to some of theintrons could not be PCR amplified suggesting that these introns arelong. The minimum daf-2 gene size based on this analysis is 33 kb.

FIG. 2A shows the predicted C. elegans DAF-2 amino acid sequence (SEQ IDNO:12. The predicted cysteine-rich region (amino acids 207–372) andtyrosine kinase domain (amino acids 1124–1398) are boxed. The signalpeptide (amino acids 1–20), proteolysis site (amino acids 806–809),transmembrane domain (amino acids 1062–1085), and PTB binding motif inthe juxtamembrane region (NPEY, amino acids 1103–1106) are underlined.Three DAF-2 tyrosine residues, Y1293, Y1296 and Y1297, in the regioncorresponding to the insulin receptor kinase Y1158 to Y1163 activationloop are likely to be autophosphorylated, based on the predictedsimilarity between the DAF-2 and insulin receptor phosphorylationtargets (FIG. 2B). Another likely target for DAF-2 autophosphorylationis the Y1106 NPEY motif located in the region corresponding to theinsulin receptor juxtamembrane region NPEY motif (at Y972), that hasbeen shown to mediate IRS-1 binding via its PTB domain to the insulinreceptor (White and Kahn, J. Biol. Chem. 269: 1–4, 1994). While DAF-2bears one YXXM motif implicated in coupling to PI 3-kinase, mammalianIRS-1 and Drosophila insulin receptor (Femandez et al., EMBO J. 14:3373–3384, 1995) bear multiple YXXM motifs. Although no p85-like adaptorsubunit has yet been detected in the C. elegans database, the AGE-1homology to mammalian p110 suggests the existence of a homologous oranalogous adaptor (Morris et al., Nature 382: 536–539, 1996). In theDAF-2 C-terminal domain, two other tyrosine residues may beautophosphorylated and bound to particular SH2-containing proteins:Y1678 binding to a PLC-g or SHP-2 homolog, and Y1686, perhaps binding toSEM-5 (FIG. 2A) (Songyang et al., Cell 72: 767–778, 1993). Whilemutations in, for example, ras and MAP kinase have not been identifiedin screens for dauer constitutive or dauer defective mutations, thesegeneral signaling pathway proteins may couple to DAF-2 as they couple toinsulin signaling in vertebrates (White and Kahn, J. Biol. Chem. 269:1–4, 1994). The predicted phosphotyrosine residues in juxtamembraneregion and the kinase domain activation loop are circled. In theextended C-terminal region, predicted phosphotyrosine residues are alsocircled and SH2-binding sites are underlined (see below).

FIG. 2B shows the cDNA encoding the C. elegans DAF-1 (SEQ ID NO:11).

FIG. 2C shows the amino acid comparison of C. elegans DAF-2 (SEQ IDNO:12) to the human insulin receptor and human IGF-I receptor (shown inparenthesis) (SEQ ID NOS:103 and 104), and to the Drosophila insulinreceptor homolog (SEQ ID NO:105), with daf-2 and human insulin receptormutations highlighted. Six daf-2 mutations map in the ligand-bindingdomain: sa187 (C347S, TGT to AGT), e1368 (S451L, TCA to TTA), e1365(A458T, GCT to ACT), sa229 (D526N, GAT to AAT), and two mutations inmg43 (C279Y, TGT to TAT and P348L, CCC to CTC). Three daf-2 mutationssubstitute conserved amino acid residues in the insulin receptor kinasedomain: sa219 (D1252N, GAT to AAT), e1391 (P1312L, CCC to CTC), ande1370 (P1343S, CCA to TCA). Darkened residues indicate amino acididentity. Hatched residues indicate amino acid similarity. Thepercentages under the domains represents the percentage of identityobserved between DAF-2 and each receptor. The corresponding BLASTprobabilities of DAF-2 random match to each protein is: 6.4×10⁻¹⁵⁷(human insulin receptor), 2.7×10⁻¹⁵⁶ (human IGF-I receptor), 2.1×10⁻¹⁵³(molluscan InR homolog), 8.3×10⁻¹⁵³ (mosquito InR homolog), 1.6×10⁻¹³⁸(human insulin receptor-related receptor), 1.7×10⁻¹²² (Drosophila InRhomolog ), 2.0×10⁻¹⁰⁸ (Hydra InR homolog). DAF-2 is more distant fromthe next most closely related kinase families: 8.9×10⁻⁵⁸ (v-ros) and3.0×10⁻⁵¹ (trkC neurotrophin receptor).

Conserved cysteine residues in the ligand-binding domain (top) aremarked with dots. In the kinase domain, active site residues thatmediate insulin receptor kinase specificity are marked with stars. Allof these residues are homologous in DAF-2. The mutations found in humanpatients are indicated at the top of the row, and daf-2 allelesubstitutions are indicated below with allele names. The sequencealignments were done with GCG programs, Pileup and Prettybox, and theidentities were calculated with the GCG program, Gap.

FIG. 3 is a photograph showing the metabolic control by C. elegans daf-2and daf-7. The top panel shows low levels of fat accumulation in a wildtype L3 animal grown at 25° C. that has been stained with Sudan black.Non-starved animals were fixed in 1% paraformaldehyde in PBS, frozen at−70° C., and freeze-thawed three times. Fixed animals were washed threetimes in PBS, and then incubated overnight in 1× Sudan black accordingto standard methods. The next panel shows higher levels of fataccumulation in daf-2(e1370) grown at the non-permissive temperature of25° C. These animals accumulate fat in both intestinal and hypodermalcells. daf-2(e1370) animals grown at 15° C., the permissive temperature,accumulate low levels of fat, like wild type (data not shown). The nextpanel shows high fat levels in the intestine and hypodermis ofdaf-7(e1372) animals grown at 25° C. The bottom panel shows high levelsof fat in daf-2(e1370) animals grown at the permissive temperature untilthe L4 stage and then shifted to the non-permissive temperature. Thisshows that daf-2 regulates metabolism without entry into the dauerstage.

FIG. 4 is a schematic diagram showing a model of insulin signaling inthe C. elegans dauer formation pathway. In the absence of dauerpheromone, an insulin-like ligand activates DAF-2, and DAF-7 TGF-β-likesignal activates the DAF-1 and DAF-4 receptors. Activated DAF-2autophosphorylates particular tyrosine residues and recruits signalingmolecules, including the PI 3-kinase homolog (a heterodimer of an as yetunidentified p85 homolog and the PI 3-kinase catalytic subunit AGE-1).The AGE-1 PI 3-kinase produces PIP3 second messenger. This secondmessenger may regulate glucose transport (White and Kahn, 1994 supra),metabolic kinase cascades that include AKT and GSK-3 (Hemmings, Science226:1344–1345, 1984; Jonas et al., Nature, 385:343–346, 1997), andtranscription and translation of metabolic genes (White and Kahn, 1994,supra). DAF-16 acts downstream of DAF-2 and AGE-1 in this pathway and isnegatively regulated by them (Vowels and Thomas, Genetics, 130:105–123,1992; Gottlieb and Ruvkun, Genetics, 137:107–110, 1994). While both theDAF-7/TGF-β and DAF-2/insulin signaling pathways converge to controldauer formation, only the DAF-2 pathway controls reproductive phaselongevity. This may be due to non-transcriptional outputs of DAF-2suggested by precedents from insulin receptor signaling. DAF-7 signalingoutput is predicted to be only transcriptional as described herein.

FIG. 5A shows that C. elegans daf-3 was genetically mapped to a regionon the X chromosome between aex-3 and unc-1. Cosmid and plasmid clonesfrom the region were assayed for transformation rescue (Mello et al.,EMBO J 10: 3959–3970,1991). Plasmid pRF4 (rol-6 transformation marker,100 ng/ml), and cosmids (5–6 ng/ml) were injected into the gonad ofdaf-7 (e1372); daf-3 (e1376) animals. Transgenic animals were scored fordauer formation at 25° C.; a dauer (i.e., a return to the daf-7phenotype) indicates rescue of daf-3; clones that rescue daf-3 areboxed. B0217 rescues the daf-3 phenotype; eighteen of nineteentransgenic lines were rescued (˜80% dauers). Examination of sequenceprovided by the C. elegans Sequencing Consortium revealed a Smadhomologous gene on B0217. A 13 kb subclone of B0217 containing just theSmad also rescues daf-3 (see FIG. 3). No rescue was seen upon injectionof other cosmids from the region, B0504 (7 lines tested, <1% rescue) andC05H10 (10 lines tested, <1% rescue). mgDf90 is a deletion that removesall of daf-3.

FIG. 5B shows the structure of the C. elegans daf-3 coding region. Thetop is the exon/intron structure of daf-3; coding exons are filledboxes, non-coding regions are open boxes, and lines are introns. daf-3cDNAs were isolated according to standard methods. Four cDNAs weresequenced completely; their N-termini are indicated by vertical lines.These three cDNAs contain ˜400 bp of 3′ UTR, but no poly-A tail; a C.elegans consensus poly-adenylation sequence is found 12 bp from the 3′end of the cDNAs. The longest of this cDNA appears full-length, as itcontains a methionine codon and the genomic sequence contains no othermethionine codon and no putative splice sites upstream before in-framestop codons. To further characterize the 5′ end of daf-3, PCR productsfrom libraries or individual daf-3 cDNAs were sequenced. From DNAisolated from a cDNA library, we amplified a product with a primer toSL1 and to a region in conserved domain I (shown as primer 1). For theindividual cDNAs, we amplified with a primer to the cDNA vector andprimer 1. These PCR products were sequenced from primer 2 to the 5′ end,and we found that there is alternative splicing at the 5′ end of daf-3,upstream of the conserved domains. The two alternate splice forms areindicated, and the ends of individual cDNAs are indicated by verticallines. Note that the second has the trans-spliced leader SL1 that isfound at the 5′ end of many C. elegans cDNAs; thus, this cDNA shows abonafide 5′ end of daf-3.

FIG. 5C shows the protein sequence alignment of C. elegans daf-3 (SEQ IDNOS:111 and 113) and the closest homolog found to date, human DPC4 (SEQID NOS:112 and 114), in the Smad conserved domains I and II. Dotsindicate gaps introduced to maximize alignment. DAF-3 is 55% identicalto DPC4 in domain I and 30% identical in domain II. daf-3(mg125) anddaf-3(mg132) mutations are indicated by boldface and underline. The Smadmutational hotspot is underlined. In addition to mg125 and mg132, sevenother daf-3 alleles were sequenced in the hotspot; none of them containsa mutation. Alleles sequenced were mg91, mg93, mg105, mg121, mg126,mg133 (isolated by A. Koweek and G. Pafferson, unpublished) and sa205.

FIGS. 6A–6G is a panel of photographs showing C. elegans DAF-3 and DAF-4expression. These photographs show GFP fluorescence, paired with DAPIfluorescence or Nomarski optics photographs, as marked. All DAF-3photographs show animals with the second plasmid from FIG. 6Aillustrates DAF-3/GFP head expression in an L1 animal. FIG. 6Billustrates DAF-3/GFP expression in the ventral nerve cord of an adultanimal. L1 animals demonstrated similar expression patterns. FIG. 6Cillustrates DAF-3/GFP expression in the intestine of an L1 animal. FIG.6D illustrates DAF-3/GFP expression in the distal tip cell of an L4animal. FIG. 6E illustrates DAF-3/GFP expression in an embryo withapproximately 200 nuclei. FIG. 6F illustrates DAF-4/GFP expression inthe head of an L1 animal. FIG. 6G illustrates DAF-4/GFP expression inthe dorsal nerve cord and ventral nerve cord of an L4 animal.

FIG. 7 is a table that shows the rescuing ability and suppression of C.elegans daf-7 by daf-3 plasmids. The solid boxes represent the Smadconserved domains I and II of daf-3; the stippled boxes represent greenfluorescent protein (GFP). For all experiments shown, daf-3 plasmidswere injected at a concentration of 10 ng/ml, and the pRF4 injectionmarker was injected at a concentration of 90 ng/ml. To score dauerformation, transgenic adult animals were allowed to lay eggs on platesfor several hours at room temperature and were then removed. The plateswere scored after two days at 25° C. The rescue experiment shows therescue of daf-7(m62); daf-3(e1376) by each of the fusion proteins.Failure to rescue results in rolling nondauers, while rescue of daf-3results in rolling dauers (the daf-7 phenotype). The control is an arraywith the pRF4 transformation marker and a non-rescuing cosmid. For eachconstruct, four or more lines were measured in two separate experiments.To measure suppression of daf-7, transgenic arrays were crossed intodaf-7 (for plasmids 1 and 3), or produced by injecting directly intodaf-7 (for plasmid 2). Transgenic (rolling) animals were scored forsuppression of daf-7 (=nondauers) or failure to suppress daf-7(=dauers). The controls are two array strains with the pRF4 marker andan unrelated GFP expressing transgene.

FIG. 8A is a photographs showing that DAF-3/GFP is associated withmetaphase chromosomes. Fixed L1 animals were immunostained with anti-GFPantibody and anti-α-tublin antibody. DNA was visualized using DAPIstaining.

FIG. 8B is a photograph showing that a truncated C. elegans daf-3/GFPprotein is predominantly nuclear. Wild-type animals were injected withthe truncated construct shown in FIG. 7 at a concentration of 10 ng/ml.The pRF4 transformation marker was injected at 100 ng/ml. The photographshows a late L1 or early L2 animal, and daf-3 is predominantly nuclear.The clear spot in the center of some of the nuclei is the nucleolus,which has no daf-3/GFP. All cells in these animals have predominantlynuclear daf-3/GFP, including the ventral cord neurons, intestinal cells,and distal tip cell (all shown), as well as head and tail neurons andhypodermal cells.

FIGS. 9A and 9B show models for the role of the C. elegansdaf-3/DAF-8/DAF-14 Smad proteins in dauer formation. FIG. 9A shows dauerreproductive growth induction. FIG. 9B shows reproductive dauer growthinduction.

FIG. 10 is a schematic illustration showing the genetic pathway thatregulates C. elegans dauer formation.

FIGS. 11A–11C show the cDNA sequences of the differentially spliced C.elegans daf-3 transcripts (SEQ ID NOS: 39, 52, and 53).

FIGS. 12A–12C show the amino acid sequences of the C. elegans DAF-3polypeptide isoforms (SEQ ID NOS: 40–42).

FIGS. 13A and 13B show the cDNA sequence of the differentially splicedC. elegans daf-16 transcripts (SEQ ID NOS: 43 and 44).

FIGS. 14A and 14B show the amino acid sequences of the C. elegans DAF-16polypeptide isoforms (SEQ ID NOS: 45 and 46).

FIG. 15 shows the cDNA sequence of the C. elegans age-1 gene (SEQ ID NO:47).

FIG. 16 shows the amino acid sequence of the C. elegans AGE-1polypeptide (SEQ ID NO: 48).

FIG. 17 is a schematic diagram illustrating that convergent TGF-β andinsulin signaling activates glucose-based metabolic genes.

FIG. 18 is a schematic diagram illustrating a switch to fat-basedmetabolism in the absence of DAF-7 and DAF-2 signals (in phermone).

FIG. 19 is a schematic diagram illustrating inhibition of the DAF-16pathway by drugs to ameliorate lack of insulin signaling.

FIG. 20 is a schematic diagram illustrating inhibition of DAF-3 by drugsto ameliorate a lack of DAF-7 signaling (for example in obesity-induceddiabetes).

FIG. 21A is an illustration showing that human FKHR (SEQ ID NO:57),FKHRL1 (SEQ ID NO:330), and AFX (SEQ ID NO:331) are the closestrelatives to DAF-16 (SEQ ID NO:45). Note that the differentially splicedDAF-16 forkhead domain (SEQ ID NO:329) is less homologous.

FIG. 21B is an illustration showing a forkhead family tree, illustratingthat DAF-16 is much more closely related to FKHR, FKHRL1, and AFX thanany other forkhead protein.

FIG. 22 is a photograph showing that daf-16 is expressed in targettissues, like daf-3. This supports the model that DAF-3 and DAF-16 arecapable of interacting.

FIG. 23 is an illustration showing a model for treatment ofobesity-induced diabetes with DAF-7 protein.

FIG. 24 is an illustration showing the genetic mapping of sup(mg144) tothe AKT genetic region.

FIG. 25 is an illustration showing the comparison of C. elegans AKT withmammalian AKT (SEQ ID NOS:87–102, 325, and 326).

FIG. 26A is a photograph showing the expression of AKT:GFP in daf-2dauers.

FIG. 26B is a photograph showing the expression of AKT:GFP in an N2adult worm.

FIG. 27 is a schematic illustration showing the molecular map of daf-16.

FIG. 28 is a graph illustrating the homology of C. elegans insulin-likemolecules (SEQ ID NOs:117–124) with human insulin (SEQ ID NO:125) and aconsensus motif (SEQ ID NO:324).

FIG. 29 is a graph illustrating a PRETTYBOX analysis of insulinsuperfamily members (SEQ ID NOS: 126–153).

FIG. 30 is a graph illustrating a PILEUP analysis of insulin superfamilymembers.

FIG. 31 is a diagram illustrating the akt-1 region. On the top is shownthe genetic and physical map of akt-1. akt-1 is contained on cosmidC12D8. Shown on the bottom is the exon/intron structure of akt-1. Codingregions are filled boxes, non-coding regions are open boxes, and intronsare lines. The pleckstrin homology domain is indicated by hatched boxes(Musacchio et al., Trends Biochem. Sci. 18:343–348, 1993). The kinasedomain is indicated in gray (Hanks and Hunter, in The Protein KinaseFacts Book Protein-Serine Kinases, eds. Hardie, G. & Hanks, S., AcademicPress, Inc., San Diego, Calif., pp. 7–47, 1995). akt-1a gene structurewas confirmed by sequencing of cDNAs. akt-1b gene structure was deducedbased on partial cDNA sequence that confirmed the exon 5 to exon 7splice and 3′UTR only.

FIG. 32 is a diagram illustrating the akt-2 region. On the top is shownthe genetic and physical maps of the akt-2 region. akt-2 is contained oncosmid R03E1. On the bottom is shown the exon/intron structure of akt-2.All symbols are as in FIG. 31. Gene structure was deduced by sequencingof a cDNA which confirmed exons 2–8 and the 3′UTR; Genefinder (Univ. ofWA) predicts exon 1.

FIG. 33 is a graph illustrating a dendogram of Akt/PKB and PKC proteinkinase families. Pileup (GCG) was used to align the entire codingsequences of the indicated proteins. C. elegans proteins are indicatedby “Ce,” rat by “r,” human by “h,” mouse by “m,” bovine by “b,” and D.melanogaster by “D.” The accession numbers for the proteins used in thePileup are contained in parentheses: CePKC2a(U82935), rPKCβ1(M19007),hAkt/PKBα(M63167), mAkt/PKB(M94335), bAkt/PKB(X61036),hAkt/PKBβ2(M95936), rAkt/PKBγ(D49836), Dakt1(Z26242). To anchor thetree, rPKCβ1 (the closest non-Akt/PKB homolog to both akt-1a andhAkt/PKBα), and CePKC2a (the closest C. elegans homolog to rPKCβ1) wereincluded in the Pileup. The Akt/PKB homologs described in this reportare indicated by the gray box.

FIG. 34 is a graph illustrating a PILEUP (GCG) analysis of AKT-1a (SEQID NO: 154), AKT-1b (SEQ ID NO: 155), AKT-2 (SEQ ID NO: 156), and humanAkt/PKBα (M63167) (SEQ ID NO: 157). Identical residues are indicated bydots, gaps introduced in order to align the sequence are indicated bydashes. The pleckstrin homology domain (Musacchio et al., TrendsBiochem. Sci. 18:343–348, 1993) is indicated by the N-terminal grayshaded areas, the kinase domain (Hanks and Hunter, in The Protein KinaseFacts Book Protein-Serine Kinases, eds. Hardie, G. & Hanks, S., AcademicPress, Inc., San Diego, Calif., pp. 7–47, 1995) is indicated by theC-terminal gray shaded areas. The mg144 Ala183Thr substitution isindicated as a T above the AKT-1a sequence. The Akt-1 and AKT-2phosphorylation sites that correspond to the hAkt/PKBα Thr308 and Ser473phosphorylation sites (Alessi et al., EMBO J. 15:6541–6551, 1996) areindicated as dots above the amino acid residue that is phosphorylated.

FIGS. 35A and 35B show the genomic sequence of pdk-1 (SEQ ID NO: 158).

FIG. 36 shows the amino acid sequence of pdk-1a (SEQ ID NO: 159).

FIG. 37 shows the amino acid sequence of pdk-1b (SEQ ID NO: 160).

FIGS. 38A–38F show metabolic control by age-1 and daf-18. Fataccumulation was assayed by Sudan Black staining in hermaphrodites grownat 20° C. The animal in FIG. 38E is a dauer larva, whereas FIGS. 38A–Dand F are comparable reproductive larval stage 4 animals. FIG. 38A showsa wild type (Bristol N2) animal. FIG. 38B shows a daf-18(e1375) animal.FIG. 38C shows an age-1(mg44)/mnC1 animal. This L4 stage larva has bothmaternal and zygotic contributions of age-1. FIG. 38D shows anage-1(mg44) animal. This L4 stage larva is a homozygote from anage-1(mg44)/mnC1 parent and has a maternal, but not zygotic,contribution of age-1. This maternal contribution of age-1 is sufficientto allow reproductive development, but the animal accumulates largeramounts of fat than the wild type or the zygotically rescued age-1mutant. FIG. 38E shows an age-1(mg44) animal. This dauer larva is aprogeny of a maternally rescued age-1(mg44) animal. The lack of maternaland zygotic contribution of age-1 causes this animal to develop as adauer and accumulate fat. FIG. 38F shows an age-1(mg44); daf-18(e1375)animal. This L4 stage larva lacks both a maternal and zygoticcontribution of age-1, but does not develop into a dauer due to thesuppression by the daf-18 mutation. The daf-18 mutation also suppressesthe accumulation of fat phenotype of the age-1 null mutant.

FIGS. 39A and 39B illustrate that daf-18 encodes a homologue of PTEN(MMAC/TEP1). FIG. 39A shows the exon/intron structure of DAF-18 (SEQ IDNOS:306, 307, 327, and 328). The phosphatase domain is indicated ingray. The bottom of this figure indicates that daf-18(e1375) has a 30base pair insertion in the fourth exon. 13 base pairs (shaded) areduplicated along with two smaller segments of the repeat (thick bars).This mutation introduces a premature stop codon (*). FIG. 39B shows analignment of the phosphatase domains of DAF-18 and PTEN (GeneBankaccession U93051) (SEQ ID NOS:308 and 309). Pileup (GCG) was used toalign the entire coding sequence. The phosphatase domain is shown withidentical amino acids shaded. The probable active site Cys-(X)₅-Argsequence is indicated with a bar.

FIGS. 40A and 40B show the amino acid and nucleic acid sequences of theC. elegans daf-18 gene (SEQ ID NOS:310 and 311).

FIG. 41 illustrates a model for the regulation of metabolism and dauerarrest by insulin receptor-like signaling. DAF-2 insulin receptor-likeactivates AGE-1 PI3K to generate PIP₃ and PI(3,4)P₂. PIP₃ and PI(3,4)P₂may activate AKT-1 and AKT-2 directly by binding to the PH domain andindirectly by regulating PDK1-mediated phosophorylation of the threonine308 equivalent site. In addition, AKT-1 may be regulated byphosphorylation at the serine 473 equivalent (AKT-2 lacks this site).DAF-18 PTEN limits AGE-1 PI3K signals by dephosphorylating PIP₃ and/orPI(3,4)P₂. In the absence of AGE-1 signals, loss of DAF-18 allows analternative source of PI(3,4)P₂ and PIP₃ to accumulate and activateAKT-1 and AKT-2. AKT-1/AKT-2 signals converge with an additionalsignaling pathway from the DAF-2 receptor to regulate the DAF-16 Forkhead transcription factor. DAF-16 responsive genes control metabolism,reproductive growth, and lifespan.

FIG. 42 shows the C. elegans cod-5 nucleic acid and amino acid sequences(SEQ ID NOS: 312 and 313).

FIG. 43 shows the C. elegans cod-5 knockout cDNA and amino acidsequences (SEQ ID NOS:314 and 315).

FIGS. 44A, 44B, and 44C show the effect of muscarinic agonists and anantagonist on dauer recovery in C. elegans and A. caninum. In FIG. 44A,oxotremorine, a synthetic muscarinic agonist, promotes dauer recovery inboth C. elegans and A. caninum. Note that daf-2(e1370) fails to recoverat all concentrations. In FIG. 44B, arecoline, a natural muscarinicagonist, promotes dauer recovery in both C. elegans and A. caninum. Notethat daf-2(e1370) fails to recover at all concentrations. FIG. 44C showsthat atropine can specifically inhibit the muscarinic agonist-inducedresponse. In C. elegans, at 1 mM oxotremorine, as the concentration ofatropine, a muscarinic antagonist, is increased, dauer recovery iscompletely inhibited. Similarly, in A. caninum larvae, arecoline andincreasing amounts of atropine cause dauer recovery to be completelyinhibited.

FIGS. 45A and 45B show that atropine specifically inhibits dauerrecovery in C. elegans and A. caninum. In FIG. 45A, wild-type N2 dauerswere placed on plates containing either bacterial food; no bacteria andno pheromone; bacteria and 1 mM atropine; or pheromone at 25 degrees. 42hours later, the plates were scored for the presence of dauers andreproductive L4/adults. With no food and no pheromone, 100% of theanimals remained arrested at the dauer stage (n>280). Addition of foodcaused efficient dauer recovery at 25 degrees. Dauers placed on plateswith food recovered efficiently, with less than 1% remaining arrested atthe dauer stage (n>1000). Addition of 1 mM atropine in the presence offood inhibited dauer recovery: 82% remained arrested at the dauer stage(n=1432). 80% of the animals maintained on plates with pheromone but nofood (n=505) remained arrested at the dauer stage. The pheromonepreparation contained bacterial contaminants that may have been used asa food source. In A. caninum incubated with 10% serum and 25 mM GSM, 9%of the infective larvae remained as dauers and did not resume feeding.Addition of atropine (0.5 mM) to the serum and GSM completely inhibitedrecovery of A. caninum L3 and no worms resumed feeding. In FIG. 45B,daf-2(e1370) and daf-7(e1372) dauers were placed onto plates at 15degrees. Animals were scored for the presence of dauers and reproductiveadults two days after food was added to the plate. Bacterial food wasadded after temperature downshift failed to induce dauer recovery indaf-2(e1370) (n=140) and daf-7(e1372) (n=36). Only 21% of thedaf-2(e1370) (n=509) and 21% of the daf-7(e1372) (n=112) dauer larvae onplates at the lower temperature with food remained as dauers after twodays. Atropine at 1 mM completely inhibited dauer recovery ondaf-2(e1370) (n=205) and daf-7(e1372) (n=166) dauers on plates at 15degrees in the presence of food.

FIG. 46 shows a model for cholinergic input induction of dauer recovery.In dauer pheromone or in a daf-7 mutant, the DAF-7 TGF-β ligand is notproduced by the ASI sensory/secretory neuron. Therefore, there is noactivation of the DAF-1 and DAF-4 TGF-β receptors or downstream DAF-8and DAF-14Smad proteins, and this results in high DAF-3 Smad activity intarget tissues. In pheromone without muscarinic agonists, no insulinlike signal is released, causing a lack of DAF-16 regulation, which incombination with unregulated DAF-3 induces dauer arrest. Under theseconditions, muscarinic stimulation causes release of an insulin-likeDAF-2 ligand which stimulates the DAF-2/AGE-1 signaling pathway toDAF-16 activation in target tissues. Since daf-7 mutants can recover inmuscarinic agonists, the TGF-β signaling pathway is not required fordauer recovery.

Under normal conditions of dauer recovery upon release from phermone andaddition of food and low temperature, these conditions may cause releaseof acetylcholine, either through the temperature or food pathways, whichbinds to the muscarinic receptor on the insulin-like signaling cell.Binding of acetylcholine to the receptor causes an increase in insulinrelease. Temperature may be coupled via the intemeurons AIY and AIZ tothe DAF-2 insulin-like signaling pathway, rather than the TGF-βsignaling pathway, because mutations in the thermoregulatory gene ttx-3can suppress mutations in daf-7 and not mutations in daf-2.

FIGS. 47A and 47B show the nucleic acid and amino acid sequences of ahuman DAF-7 homologue (SEQ ID NOS: 316 and 317).

THE DAF-2 INSULIN RECEPTOR FAMILY MEMBER REGULATES LONGEVITY ANDDIAPAUSE IN C. ELEGANS

Arrest at the C. elegans dauer stage is normally triggered by adauer-inducing pheromone detected by sensory neurons which signal via acomplex pathway to target tissues that are remodeled and metabolicallyshifted such as the germ line, intestine, and ectoderm (Riddle, In:Caenorhabditis elegans II, D. Riddle, T. Blumenthal, B. Meyer, J.Priess, eds., Cold Spring Harbor Laboratory, Cold Spring Harbor, N.Y.,1997, pp. 739–768. Kenyon, op cit., pp. 791–813.). Genetic epistasisanalysis of daf mutants that arrest at the dauer stage or enter thereproductive life cycle independent of pheromone regulation has revealedparallel genetic pathways that regulate distinct aspects of the dauermetamorphosis (Vowels and Thomas, Genetics 130: 105–123, 1992; Gottlieband Ruvkun, Genetics 137: 107–120, 1994). The pathway that includesdaf-2 is unique in that it controls both reproductive development andnormal senescence: daf-2 mutant animals arrest development at the dauerlarval stage and have dramatically increased longevity (Table I)(Riddle, In: Caenorhabditis elegans II, D. Riddle, T. Blumenthal, B.Meyer, J. Priess, eds., Cold Spring Harbor Laboratory, Cold SpringHarbor, N.Y., 1997, pp. 739–768; Kenyon, op cit. pp 791–813; Vowels andThomas, Genetics 130: 105–123, 1992; Gottlieb and Ruvkun, Genetics 137:107–120, 1994; Larsen et al., Genetics 139: 1567–1583, 1995; Kenyon etal., Nature 366: 461–464, 1993; Dorman et al., Genetics 141: 1399–1406,1995).

Table I shows the percentage of dauer formation of daf-2 alleles and theassociated mutations. Eggs from animals grown at 15° C. (day 0) wereincubated at 15, 20, or 25° C. Numbers in parenthesis are animalscounted. Numbers of wild-type animals and dauers were counted on day 3(20° C. and 25° C.) or day 5 (15° C.). Most of the dauers marked withstars recovered by day 4 (sa229 at 25° C.) or by day 8 (sa229) and sa219at 15° C., e1368 and sg219 at 20° C., and e1365 and e1368 at 25° C.).mg43 was studied as follows: dpy-1(el)daf-2(mg43); SDP3 animals weregrown at 20° C. until the young adult stage. Eggs from five adults werelaid at 15° C. or 20° C. and grown at the same temperatures. Numbers ofDpy-Daf animal and Dpy-non-Daf animals were counted on day 3 (20° C.) orday 5 (15° C.). Sg187 and sg229 were also studied by Malone and Thomas(Genetics 136:879–886, 1994).

TABLE I Percentage of dauer formation of daf-2 alleles % dauer formationRegion Allele mutation 15° C. 20° C. 25° C. cys-rich mg43 C279Y& 100.0(215) 100.0 (245) n.d. P348L sa187 C347S  0.4 (461)  98.7 (224) 100(910) ligand- e1368 S451L  0.0 (328)  4.5* (418)  99.7* (698) bindinge1365 A458T  0.0 (450)  0.0 (461)  99.4* (814) kinase sa229 D526N  3.4*(234) n.d.  22.1* (420) sa219 D1252N  10.0* (460)  99.7* (396) 100 (514)e1391 P1312L  3.3 (332) 100 (323) 100 (322) e1370 P1343S  0.0 (520)  0.0(188) 100 (635)

Genetic mapping using both visible genetic markers and restrictionfragment length polymorphism (RFLP) markers places daf-2 between mgP34and mgP44 (FIG. 1). While cosmid coverage of this physical geneticregion is not complete, YAC Y53G8 carries the genomic region thatincludes mgP34 and mgP44, which flank daf-2 (FIG. 1). As a step in theC. elegans genome sequencing effort, random M13 subclones derived fromY53G8 were sequenced by the Genome Sequencing Center.

Sequence Identities Show that DAF-2 is Likely to Bind to an Insulin-likeLigand and to Phoshorylate Tyrosine Residues

The amino acid sequences and nucleotide sequences encoding DAF-2 areshown in FIGS. 2A and 2B, respectively. Using BLASTX to compare 570translated Y53G8 M13 subclone sequences against the Genbank proteindatabase, we found that four sequences are homologous to the mammalianinsulin receptor family. An insulin receptor was a good daf-2 candidategene because insulin regulates vertebrate growth and metabolism (Whiteand Kahn, J. Biol. Chem. 269: 1–4, 1994), and because aphosphatidylinositol (PI) 3-kinase has been shown to act in both theinsulin receptor and daf-2 pathways (White and Kahn, J. Biol. Chem. 269:1–4, 1994; Morris et al., Nature 382: 536–539, 1996). The detection ofmultiple daf-2 mutations in the gene (see below), and the coincidence ofthe genetic location of this insulin receptor homolog with daf-2 (FIG.2C) establish that this insulin receptor homolog corresponds to daf-2.

The daf-2 transcription unit and gene structure were determined usingPCR primers derived from daf-2 genomic subclone sequences to amplifydaf-2 genomic and cDNA regions. A probable full length daf-2 cDNA bearsa 5172 base open reading frame, a 485 base 5′ UTR and a 159 base 3′ UTR(FIGS. 1, 2A). The predicted DAF-2 protein shows long regions ofsequence identity to the insulin receptor family. Over the entireprotein, DAF-2 is 35% identical to the human insulin receptor (Ebina etal., Cell 40: 747–58, 1985; Ullrich, et al., Nature 313: 756–61, 1985),34% identical to the human IGF-I receptor (Ullrich, et al., EMBO J.: 5,2503–12, 1986), and 33% identical to the human insulin receptor-relatedreceptor (Shier and Watt, J. Biol. Chem. 264: 14605–8, 1989). DAF-2 isthe only member of the insulin receptor family in the 90 Mb C. elegansgenome sequence (about 90% complete) or in the 10 Mb C. elegans ESTsequence database. Because it is equally distant from insulin, IGF-I,and insulin receptor-related receptors, DAF-2 is probably the homolog ofthe ancestor of these duplicated and diverged receptors, and thus maysubserve any or all of the functions of these mammalian receptors (seebelow). Like these receptors, DAF-2 has a putative signal peptide, acysteine-rich region in the putative ligand binding domain, a putativeproteolysis site, a transmembrane domain, and a tyrosine kinase domain.In addition, DAF-2 has a C-terminal region that may serve a functionsimilar to the mammalian insulin receptor substrate-1 (IRS-1) (FIG. 2;White and Kahn, J. Biol. Chem. 269: 1–4, 1994).

In the approximately 500 amino acid ligand-binding domain of the insulinreceptor, DAF-2 is 36% identical to insulin receptor and 35% identicalto the IGF-I receptor. Twenty-one of twenty-three phylogeneticallyconserved cysteine residues in this domain are conserved in DAF-2 (FIG.2C). The DAF-2 cys-rich region is 34% identical to human insulinreceptor and 28% identical to the IGF-I receptor. Six daf-2 mutationsmap in this domain (FIG. 2C, Table I). The mg43 and sa187 mutationssubstitute conserved residues in the cys-rich region (FIG. 2C).daf-2(mg43) carries two mutations which substitute conserved residues,which may explain the strength of this allele (non-conditional, TableI). Other substitutions at non-conserved residues cause less severephenotypes (Table I). Insulin resistant and diabetic patients withmutations in the ligand binding domain of the human insulin receptorgene have been identified (Taylor, Diabetes 41: 1473–1490, 1992) (seebelow). These mutations impair receptor transport to cell surface, orinsulin binding affinity, or both. The DAF-2 mutations in this domainmight similarly decrease receptor signaling to cause dauer arrest.

Insulin receptors are α2,β2 tetramers proteolytically processed from asingle precursor protein (White and Kahn, J. Biol. Chem. 269: 1–4,1994). DAF-2 bears a probable protease recognition site at a positionanalogous to the insulin receptor processing site (RVRR 806-809)(Yoshimasa et al., J. Biol. Chem. 265: 17230–17237, 1990).

The 275 amino acid DAF-2 tyrosine kinase domain is 70% similar and 50%identical to the human insulin receptor kinase domain. Upon insulinbinding, the intracellular tyrosine kinase domain of the insulinreceptor phosphorylates particular tyrosine residues flanked bysignature amino acid residues (upstream acidic and downstreamhydrophobic amino acids (Songyang and Cantley, Trends Biochem. Sci. 20:470–475, 1995)) in the intracellular domain as well as on IRS-1 (Whiteand Kahn, J. Biol. Chem. 269: 1–4, 1994). Multiple DAF-2 tyrosineresidues in these sequence contexts are likely autophosphorylationtargets, including three tyrosines in a region similar to the insulinreceptor activation loop and one in the juxtamembrane region asdescribed above (FIG. 2C). Based on the crystal structure of the insulinreceptor kinase domain bound to its activation loop, eight kinase domainresidues mediate target site specificity (Hubbard et al., Nature 372:746–754, 1994). In DAF-2 (but not in more distantly related receptorkinases), these residues are invariant (5/8) or replaced with similaramino acids (3/8: K to R, E to D) (FIG. 2C), suggesting that DAF-2phosphorylates the same target tyrosine motifs as the insulin receptorkinase.

Three daf-2 missense mutations substitute conserved amino acid residuesin the kinase domain (FIG. 2C, Table I). All three mutations causemoderate to strong dauer constitutive phenotype, but none are as strongas the non-conditional alleles, for example, mg43 (Table I). Humaninsulin receptor mutations in the kinase domain exhibit decreased kinaseactivity and cause severe insulin resistance and associated defects(FIG. 2C; Taylor, Diabetes 41: 1473–1490, 1992). Remarkably, a humandiabetic insulin resistant patient bears the same amino acidsubstitution (P1178L) as daf-2(e1391) (Kim et al., Diabetologia 35:261–266, 1992). This patient was reported to be heterozygous for thissubstitution. daf-2(e1391) is not dominant whereas it is a highlypenetrance recessive mutation (Table I).

To test for dominance of daf-2(e1391), using a genetically markedbalancer chromosome, 105 dauers segregated from 485 daf-2/+ parents asexpected for a recessive mutations. The genotype of 76/77 of theseanimals was homozygous daf-2(e1391) whereas 1/77 of the dauers wasdaf-2(e1391)/+, indicating a less than 1% dominance. It is possible thatin contrast to C. elegans, the P1178L mutation in humans is dominant, orthat the patient carries a second insulin receptor mutation in trans, orcarries mutations in other genes (for example, other complex type IIdiabetes loci) that enhance the dominance of P1178L (Bruning et al.,Cell 88: 561–572, 1997).

AGE-1 PI 3-kinase is a Major DAF-2 Signaling Output

Like the Drosophila insulin receptor homolog, DAF-2 has a longC-terminal extension that may function analogously to mammalian IRS-1(Fernandez et al., EMBO J. 14: 3373–3384, 1995). In mammals, IRS-1tyrosine residues are phosphorylated by the insulin receptor kinase, andthese phosphotyrosines mediate binding to a variety of signalingproteins bearing SH2 domains (White and Kahn, J. Biol. Chem. 269: 1–4,1994; Songyang et al., Cell 72: 767–778, 1993.). Many, but not all, ofthe DAF-2 C-terminal extension tyrosines bear flanking sequence motifssuggestive that they are autophosphorylated (FIG. 2A; Songyang andCantley, Trends Biochem. Sci. 20: 470–475, 1995). Based on precedentsfrom IRS-1 interactions with mammalian PI 3-kinases (White and Kahn, J.Biol. Chem. 269: 1–4, 1994), a YXXM motif at DAF-2 Y1504 is likely tomediate interaction with the AGE-1 PI 3-kinase, which acts in the samegenetic pathway as daf-2 (FIG. 4) (Morris et al., Nature 382: 536–539,1996).

Three DAF-2 tyrosine residues, Y1293, Y1296 and Y1297, in the regioncorresponding to the insulin receptor kinase Y1158 to Y1163 activationloop are likely to be autophosphorylated, based on the predictedsimilarity between the DAF-2 and insulin receptor phosphorylationtargets (FIG. 2C). Another likely target for DAF-2 autophosphorylationis the Y1106 NPEY motif located in the region corresponding to theinsulin receptor juxtamembrane region NPEY motif (at Y972), that hasbeen shown to mediate IRS-1 binding via its PTB domain to the insulinreceptor (White and Kahn, J. Biol. Chem. 269: 1–4, 1994). While DAF-2bears one YXXM motif implicated in coupling to PI 3-kinase, mammalianIRS-1 and Drosophila insulin receptor (Fernandez et al., EMBO J. 14:3373–3384, 1995) bear multiple YXXM motifs. Although no p85-like adaptorsubunit has yet been detected in the C. elegans database, the AGE-1homology to mammalian p110 suggests the existence of a homologous oranalogous adaptor (Morris et al., Nature 382: 536–539, 1996). In theDAF-2 C-terminal domain, two other tyrosine residues may beautophosphorylated and bound to particular SH2-containing proteins:Y1678 binding to a PLC-γ or SHP-2 homolog, and Y1686, perhaps binding toSEM-5 (FIG. 2A) (Songyang et al., Cell 72: 767–778, 1993). Whilemutations in, for example, ras and MAP kinase have not been identifiedin screens for dauer constitutive or dauer defective mutations, thesegeneral signaling pathway proteins may couple to DAF-2 as they couple toinsulin signaling in vertebrates (White and Kahn, J. Biol. Chem. 269:1–4, 1994).

The insulin receptor also couples to other signaling pathways (White andKahn, J. Biol. Chem. 269: 1–4, 1994); analogous DAF-2 phosphotyrosineresidues may mediate these interactions (as described above). Thus, wesuggest that tyrosines in the DAF-2 cytoplasmic domain areautophosphorylated upon ligand binding, and recruit the AGE-1 PI-3kinase homolog (as well as other molecules) to signal reproductivedevelopment and normal senescence.

Metabolic Control by daf-2 in Control of Diapause and Aging

Insulin and its receptor families play key roles in vertebrate (and byour evidence in invertebrates) metabolic and growth control (Kahn andWeir, eds., Joslin's Diabetes Mellitus, Lea & Febiger, 1994). Uponinsulin release—by increasing blood glucose and autonomic inputs—insulinreceptor engagement directs a shift in the activities of key metabolicenzymes, as well as changes in the transcription and translation ofmetabolic regulators in fat, liver, and muscle cells, all of which leadto assimilation of glucose into glycogen and fat (White and Kahn, J.Biol. Chem. 269: 1–4, 1994). IGF-I is released from the liver inresponse to pituitary growth hormone, and mediates many of the growthand development responses to that endocrine signal (Mathews et al., ProcNatl Acad Sci. U.S.A. 83: 9343–7, 1986). Interestingly, lifespan isdramatically increased in dwarf mice with defects in growth hormonesignaling, and presumably decreased IGF-I signaling as well (Brown-Borget al., Nature 384: 33, 1996). No function for the insulinreceptor-related receptor has yet been established, though it isexpressed in conjunction with NGF receptor (Reinhardt et al., J.Neurosci. 14: 4674–4683, 1994).

Diapause arrest in general and dauer arrest in particular are associatedwith major metabolic changes (Tauber et al., Seasonal Adaptation ofInsects, Oxford University Press, New York, N.Y., 1986), consistent witha model that daf-2 acts in a metabolic regulatory pathway related toinsulin signaling. In wild-type animals, DAF-2 signaling allowsnon-dauer reproductive growth, which is associated with utilization offood for growth in cell number and size, and small stores of fat (FIG.3). In daf-2 mutant animals, metabolism is shifted to the production offat (FIG. 3) and glycogen (data not shown) in intestinal and hypodermalcells. Even when a temperature-sensitive daf-2 mutant allele is shiftedto the non-permissive temperature at the L4 or adult stage (after thecritical period for daf-2 control of dauer formation), metabolism isshifted towards storage of fat (FIG. 3). Thus daf-2 also regulatesmetabolism during reproductive development. Similar metabolic shifts areseen in wild-type pheromone-induced dauers (data not shown), age-1mutants (data not shown), and daf-7 mutants (FIG. 3). In support of thismetabolic shift, in dauer larvae, enzymes that regulate glycolysis aredown-regulated while those that regulate glycogen and fat synthesis areup-regulated, and there is ultrastructural evidence for increased lipidand glycogen (O'Riordan and Burnell, Comp. Biochem. & Physiol. 92B:233–238, 1989; O'Riordan and Burnell, Comp. Biochem. & Physiol. 95B:125–130, 1990; Popham and Webster, Can. J. Zool. 57: 794–800, 1978;Wadsworth and Riddle, Develop. Biol. 132: 167–173, 1989). The dauermetabolic shift is associated with arrest of germ line proliferation,and arrest of somatic cell division and enlargement (Riddle, In:Caenorhabditis elegans II, D. Riddle, T. Blumenthal, B. Meyer, J.Priess, eds., Cold Spring Harbor Laboratory, Cold Spring Harbor, N.Y.,1997, pp. 739–768; Kenyon, op cit., pp. 791–813).

There is precedent for insulin-like signaling in invertebrate metabolicand growth control: insulin-like growth factors have been detected inmetabolism-regulating ganglia in molluscs (Roovers et al., Gene 162:181–188, 1995) and regulate molting in locust (Hetru et al., Eur. J.Biochem 201: 495–499, 1991) and silkworm (Kawakami et al., Science 247:1333–1335, 1990). Consistent with the daf-2 regulation of diapause,injection of insulin into diapausing Pieris brassicae (an insect) pupaeinduces recovery (Arpagaus, Roux's Arch. Dev. Biol. 196: 527–530, 1987).

Without being bound to a particular theory, we hypothesize that aninsulin-like signal is up-regulated during reproductive development andstimulates DAF-2 receptor autophosphorylation and recruitment of theAGE-1 PI 3-kinase to produce the second messenger PIP3. AGE-1 is likelyto be a major signaling output of DAF-2 because of the similarity of theage-1 and daf-2 mutant phenotypes and because of their similar placementin the epistasis pathway (Vowels and Thomas, Genetics 130: 105–123,1992; Gottlieb and Ruvkun, Genetics 137: 107–120, 1994). Precedents frominsulin receptor signaling suggest the following candidate targets forDAF-2/AGE-1/PIP3 regulation of metabolism: (1) membrane fusion ofvesicles bearing glucose transporters (Kahn and Weir, eds., Joslin'sDiabetes Mellitus, Lea & Febiger, 1994) (or more probably trehalosetransporters (Tauber et al., Seasonal Adaptation of Insects, OxfordUniversity Press, New York, N.Y., 1986)) to facilitate flux of thismolecule for growth and reproductive metabolism; (2) PIP3 activates anAKT/GSK-3 kinase cascade (Hemmings, Science 275: 628–630, 1997) whichmay regulate the activities of glycogen and fat synthetic and lyticenzymes; (3) transcription and translation of metabolic genes such asPEPCK, GDH, fat synthetases, and lipases (White and Kahn, J. Biol. Chem.269:1–4, 1994). Genetic epistasis analysis suggests that DAF-2/AGE-1signaling negatively regulates daf-16 gene activity (Vowels and Thomas,Genetics 130: 105–123, 1992; Gottlieb and Ruvkun, Genetics 137: 107–120,1994). DAF-16 could act at any point downstream of AGE-1 in thissignaling pathway. Evidence is presented herein that DAF-16 representsthe major transcriptional output to DAF-2/AGE-1 PIP3 signaling.

In addition to these metabolic changes, the DAF-2 signaling cascade alsocontrols the reproductive maturation of the germ line as well asmorphogenetic aspects of the pharynx and hypodermis (Riddle, In:Caenorhabditis elegans II, D. Riddle, T. Blumenthal, B. Meyer, J.Priess, eds., Cold Spring Harbor Laboratory, Cold Spring Harbor, N.Y.,1997, pp. 739–768; Kenyon, op cit., pp. 791–813). The DAF-2 receptor mayact, for example, in the hypodermal and intestinal target tissues wherewe note a change in metabolism triggered by the dauer regulatory cascade(FIG. 3). It is also possible that DAF-2 regulates the metabolism andremodeling of tissues indirectly, for example, by controlling theproduction of other hormones (Nagasawa et al., Science 226: 1344–1345,1984; Jonas, et al., Nature 385: 343–346, 1997). Expression and geneticmosaic analysis of daf-2 is essential to distinguish these models.

Even though DAF-2 and the mammalian insulin receptor both regulatemetabolism, the metabolic defects associated with mutations in thesereceptors appear to be different. Complete loss of mammalian insulinreceptor activity causes growth arrest at birth (Leprechaunism inhumans), and a metabolic shift to runaway lipolysis and ketoacidosis(Kahn and Weir, eds., Joslin's Diabetes Mellitus, Lea & Febiger, 1994),rather than the fat accumulation we observe in daf-2 mutants (FIG. 3).This distinction between insulin receptor and daf-2 mutants may reflectdistinct metabolic responses to this signaling, or a difference betweencomplete loss and declines in insulin signaling. In humans, ketoacidosisis only induced during severe starvation or pathological states wheninsulin levels are very low (Kahn and Weir, eds., Joslin's DiabetesMellitus, Lea & Febiger, 1994). Since none of the daf-2 mutationsdescribed herein are clear null mutations, it is possible that daf-2dauer-constitutive alleles are more analogous to non-null human insulinreceptor mutations. Most daf-2 alleles are temperature sensitive,including alleles isolated in genetic screens that would allow therecovery of non-temperature sensitive mutations (Vowels and Thomas,Genetics 130: 105–123,1992; Gottlieb and Ruvkun, Genetics 137: 107–120,1994). Substitutions of DAF-2 amino acid residues conserved acrossphylogeny cause more penetrant dauer arrest at all temperatures thansubstitutions of non-conserved residues. daf-2 mutants that arrestdevelopment at the dauer stage independent of growth temperature arelikely to have the least gene activity (for example mg43). Several daf-2alleles also cause 5% to 10% embryonic lethality (unpublished results),suggesting that daf-2 functions during embryonic development. None ofthe daf-2 mutations detected so far are nonsense, frameshift, ordeletion alleles. It is possible that the daf-2 null phenotype isstronger than non-conditional dauer arrest, for example embryoniclethality. However, dauer constitutive daf-2 mutant alleles are isolatedfrom EMS mutagenesis at a very high rate (about 1/300 chromosomes),suggesting that the existing alleles are not rare viable alleles. Infact, the 14 year old patient with the same insulin receptor mutation asdaf-2(e1391) was morbidly obese (Kim et al., Diabetologia 35: 261–266,1992), suggesting that metabolic effects of decreased insulin signalingmay be similar to daf-2 mutants.

It may be significant to human diabetes that animals carrying mutationsin daf-16 can grow reproductively even if they also carry daf-2 andage-1 mutations that disable insulin-like metabolic control signals(Vowels and Thomas, Genetics 130: 105–123, 1992; Gottlieb and Ruvkun,Genetics 137: 107–120, 1994). These data suggest that it is unregulateddaf-16 gene activity that causes these metabolic shifts. The analogousmetabolic defects associated with both type I and type II diabetes maybe caused by similar unregulated activity of the human DAF-16 homolog.Below we disclose the molecular identity of daf-16. Inhibition of itsactivity is expected to ameliorate the metabolic dysregulationassociated with insulin signaling defects.

DAF-16 Encodes a Forkhead Transcription Factor Homolog

Using a combination of genetic mapping and detection of multiple daf-16mutations in a 5 kb region, we have determined the nucleic acid sequenceof daf-16. daf-16 was mapped 1 map unit to the left of lin-11 and 3.3map units right of unc-75 on Chromosome I. This region of the genomecontained a gap that was not covered by cosmids nor YACs. We used afosmid library (Genome Sciences, Inc.) to walk into the gap. Sequenceanalysis of the ends of four fosmids (H27K20, H01H03, H12I08, andH35K06) revealed that the previously unmapped contig 133 lies in thelin-11 unc-75 gap. Cosmids from the approximate daf-16 genetic locationwere used to detect RFLPs between C. elegans strains Bristol N2 andBergerac RC301: mgP45 on cosmid C39H11, mgP46 on cosmid F28D9, mgP49 oncosmid C35E7, mgP50 is on cosmid C43H8. Zero out of 30 daf non-Uncrecombinants carry the RC301 alleles of mgP45 and mgP50. Two out of 30Daf non-Unc recombinants carry the RC301 allele of mgP49. 10 out of 30Daf non-Unc recombinants carry the RC301 allele of mgP46. 1 out of 4non-Lin Daf recombinants carry the N2 allele of mgP45. 4 out of 4non-Lin Daf recombinants carry the N2 allele of mgP49. These dataindicate that daf-16 lies between cosmids C43H8 and C35E7. The daf-16gene was identified by identifying deletions (mgDf50) and pointmutations (mg53 and mg54) within the forkhead gene on the cosmid R13H8(FIG. 27). There are two major daf-16 transcripts whose sequences areshown in FIG. 13A and FIG. 13B (SEQ ID NOS: 43 and 44, respectively).The amino acid sequences coding for the DAF-16 isoforms are shown inFIGS. 14A–14C (SEQ ID NOS: 44–46).

We have detected three daf-16 mutations: (1) a large deletion ofconserved regions in daf-16 (mg ΔF50) that proves that the daf-16 nullphenotype is a suppression of daf-2 mutations; (2) a S to L substitutionin exon 6 in daf-16 (mg 53) that alters a conserved WKNSIRH motif; and(3) a nonsense mutation in exon 3 in daf-16 (mg 54) that is predicted totruncate one of the daf-16 differentially spliced isoforms.Interestingly, this spliced isoform has a distinct forkhead DNA bindingdomain and is therefore expected to bind to distinct promoters orcombinatorial partners. This mutant is a weak suppressor of daf-2,suggesting that both DAF-16 isoforms are necessary for metaboliccontrol.

Sequence analysis has revealed that DAF-16 is a member of the forkhead(FH) transcription factor family (FIGS. 21A–21B). This strong amino acidhomology indicates that DAF-16 is a transcription factor. Our geneticanalysis indicates that DAF-16 activity is regulated by the DAF-2/AGE-1insulin signaling pathway. Precedent from another receptor kinasesignaling pathway endorses this model: the C. elegans LIN-31 forkheadprotein has been shown to be regulated by a tyrosine kinase signalingcascade from the LET-23 EGF receptor homolog (Kim, Genes Dev. 7:933–947, 1993). Consistent with a model that DAF-16 acts downstream ofinsulin signaling, forkhead transcription factors have also beenimplicated in metabolic regulation: another FH family member ismammalian HNF-3, an endoderm-specific transcription factor that acts atthe same metabolic control protein promoters as HNF-1 and HNF-4, both ofwhich are mutant in maturity onset diabetes of the young (MODY)(Yamagata et al., Nature 384: 455–458, 1996; Yamagata et al., Nature384: 458–460, 1996).

The identification of DAF-16 as a forkhead transcription factor alsoexplains much of the complex daf genetics of C. elegans. The convergenceof DAF-7 TGF-β-like signaling and DAF-2 insulin-like signaling is alsoexplained by our discovery that DAF-16 is a FH protein and DAF-3 is aSmad protein: Precedent for an interaction between Smad and forkheadproteins has been found in Xenopus. Response to the TGF-β superfamilyrelative activin in early frog development is mediated by an interactionbetween the distant relative of DAF-16 called FAST-1, and the Smadprotein, Smad2 (Nature 383: 600–608, 1996). These proteins bind to anenhancer element that is very similar to the myosin II promoter to whichDAF-3 binds (see below). Thus our molecular and genetic data indicatethat the DAF Smad proteins and DAF-16 FH protein interact on metaboliccontrol promoters.

Interestingly, analogously to daf-16 bypass of the need for DAF-2insulin receptor signaling in daf-16 mutant animals, lin-31 mutationssuppress the need for LET-23 EGF signaling in C. elegans vulvaldevelopment. These findings indicate that the DAF-2 receptor, adownstream signaling molecule (AGE-1), and a transcription factor targetDAF-16 are involved in insulin-like signaling in C. elegans development.Without being bound by any particular theory, we hypothesize that C.elegans insulin signaling via DAF-2 and AGE-1 activate DAF-16transcriptional activity, so that in a daf-2 or age-1 mutant, or indauer pheromone, DAF-16 acts as a repressor protein causing a metabolicshift to fat metabolism. Our analysis of daf-16 expression shows that,like DAF-3, it is expressed in target tissues (FIG. 22). Our evidenceindicates that Smad protein transcription factors (e.g., DAF 3, DAF8,DAF14) and DAF-16 act on a common set of promoters as combinatorialtranscriptional regulators. Thus, it is at these metabolic genes thatDAF-7 and TGF-β-like and DAF-2 insulin-like signals converge to controlmetabolism. In addition, our evidence indicates that in the presence ofDAF-2 signaling (mimicking high insulin), DAF-16 acts as an activator oftranscription, causing a shift in metabolism toward glucose utilizationfor cell growth. The molecular analysis described herein suggests thatlack of daf-16 gene activity completely bypasses the need for insulinsignaling in metabolic control by releasing metabolic control fromDAF-16 repression. These data suggest that if a human DAF-16 homologacts downstream of insulin signaling in humans, drugs could be developedthat inhibit its activity to bypass the need for insulin signaling.Identification of a such a drug should provide a means for treating bothType I and Type II diabetes.

As shown in FIGS. 21A–21B, the human FKHR, FKHRL1, and AFX genes,identified as oncogene breakpoints but not as insulin signaling genes,are much more closely related to DAF-16 than the next closest relativein either Genbank or in the 94% complete C. elegans genome sequence.These data indicate that FKHR, FKHRL1, and AFX are excellent candidatesfor subserving the same function as C. elegans DAF-16: transduction ofinsulin signals and convergence with DAF-7-like Smad signals.

Evidence for the C. elegans AKT Kinase as the Probable Output ofDAF-2/AGE-1 Signaling

We screened genetically for mutations that bypass the need for age-1signaling. This was done by mutagenizing a strain carrying anage-1(mg44) null mutation (this mutation was heterozygous to allow thestrain to grow). After two generations, animals that could survivewithout age-1 gene activity were selected by their lack of arrest at thedauer stage. We identified daf-16 mutations, as expected. However, wealso identified two new gain of function mutations, sup(mg142) andsup(mg144).

sup(mg144) suppresses three different age-1 alleles, indicating thatthis mutation bypasses the need for AGE-1 production of PIP3. Forexample, sup(mg144) suppresses the dauer arrest of age-1(mg44), (m333),(mg109) such that fertile adults are formed. sup(mg144) does notsuppress the lack of insulin signaling in the daf-2 mutant:daf-2(e1370); sup(mg144) form dauers at 25 degrees. This suggests thatnot all of the DAF-2 signaling output is via AGE-1. However, in theabsence of both DAF-2 and AGE-1 signaling, sup(mg144) weakly suppresses,allowing some fertile adults to bypass arrest at the dauer stage.daf-2(e1370); sqt-1 age-1(mg44); sup(mg144) form 8% fertile adults, 12%sterile adults, and 80% dauers at 25 degrees.

Interestingly, sup(mg144) is a dominant suppressor of age-1 mutations.sqt-1 age-1(mg44); sup(mg144)/+form 100% fertile adults. The sup(mg144)parental genotype does not affect this outcome. This data indicates thatsup(mg144) is a dominant activating or dominant inactivating mutation.

Genetic mapping indicates that sup(mg144) may identify an activatingmutation in the C. elegans AKT homologue (FIG. 25). By placingsup(mg144) in trans to a multiply marked chromosome (using PCR basedRFLPs), we found that sup(mg144) maps to a 2 map unit genetic intervalthat includes C. elegans AKT (FIG. 24).

In particular, 2/39 sup(mg144) homozygous animals isolated from asup(mg144)/polymorphic Bergerac chromosome parent recombined betweensup(mg144)mg144 and stP6 (these animals also carried stP18). In thisexperiment mg144 was a heterozygote with RW7000 for three generations,thus placing sup(mg144) approximately 2.2 mu to the left of stP6.

In addition, 1/39 sup(mg144) homozygous animals isolated from asup(mg144)/polymorphic Bergerac chromosome parent recombined betweensup(mg144) and bP1. In this experiment mg144 was a heterozygote withRW7000 for two generations. Accordingly, this number is approximately1/80 or 1.2 mu from bP1.

We generated a GFP fusion to AKT and showed that this gene is expressedat high levels in dauer larvae but at much lower levels and in fewercells in wild type animals. (FIGS. 26A–26B) Thus AKT represents a dauerregulated gene that may respond to DAF-16 and DAF-3 transcriptionalcontrol. Multiple probable binding sites, related to the DAF-3 bindingsite in myoII have been identified.

Sup(mg142) Identifies Another Likely Output of Age-1 Signaling

mg142 suppresses three different age-1 alleles (age-1(mg44),age-1(m333), and age-1(mg109) at 20 degrees. age-1(mg44); sup(mg142)form fertile adults at 15 and 20 degrees. At 25 degrees, they form 33%fertile adults and 67% sterile adults.

sqt-1 age-1(mg44); mg142/+ form 14% fertile adults and 86% sterileadults when the parent was homozygous for mg142. sqt-1 age-1(mg44);mg142/+ form 67% fertile adults and 33% sterile adults when the parentwas heterozygous for mg142. daf-2(e1370); mg142 form sterile adults at25 degrees; daf-2(e1370); sqt-1 age-1(mg44); mg142 form sterile adultsand dauers at 25 degrees. Preliminary mapping places mg142 approximately1 .6mu to the left of unc-1 on LGX.

Novel C. elegans Insulin-like Hormones are Probable DAF-2 Ligands

Mutations in daf-2 not only cause a metabolic shift, but also affectlongevity of C. elegans. The nearly complete C. elegans genome sequenceallowed a definitive search for insulin superfamily members to beperformed, and, in this search, we detected multiple insulin-relatedproteins in the C. elegans genome database. When insulin, IGF-I, orIGF-II were compared to the translated worm genome sequence, this largeset of insulin superfamily members was not detected. However, when thesearch was carried out with the conserved signature residues shown belowthat are the hallmark of the insulin superfamily (SEQ ID NOS: 115, 116),as now defined, we detected a number of novel insulin molecules.

Conserved Insulin Motifs

-   1 LCGXXLVEALXXVCGXRGFFYTPKTRRKRGIVEQCCXXXCXXXQL EXYCN 50 (SEQ ID NO:    115); and-   1 aanqrLCGRHLADALYFVCGNRGFfyspkgGIVEECCHNPCTLYQLE NYCn 51 (an    insulin superfamily consensus from the Blocks database at    www.blocks.fhcrc.org; SEQ ID NO: 116).-   The insulin superfamily signature residues were assembled using a    set of vertebrate insulins and IGF-I and II proteins as well as silk    moth bombyxin (a distant insulin relative) and a Limulus insulin    superfamily member. The use of superfamily signature amino acid    positions to detect distant relatives in databases is a more    definitive approach to ascertaining gene superfamily members than    simple searches with single family members.

Using these motifs, eight novel C. elegans insulin superfamily memberswere identified (SEQ ID NOS: 117–124), the coding sequences of which areshown in FIG. 28. In this Figure, the family members are named from thecosmid genomic DNA sequences from which they were detected. All of theseinsulins have A and B peptide homology to the insulin superfamily, andsome of them have conserved dibasic processing sites that would mediateprocessing of the intervening unconserved C peptide. These genes arewidely distributed on the C. elegans genome, although some are clustered(for example, ZK75.1, ZK75.2, ZK75.3, and ZK84.6). More distant insulinrelatives may exist, but these are likely to engage receptors other thanDAF-2.

Of the isolated insulin superfamily members, F13B12 was most closelyrelated to human insulin and IGF-I, II. This was especially obvious froma PILEUP analysis in which a phylogenetic tree of protein superfamilymembers was constructed (FIGS. 29 and 30). The insulin product of F13B12clustered more closely to the mammalian insulin and IGF-I,II proteinsthan to other distant relatives like relaxin. Relaxin defined the mostdistantly related insulin superfamily member in the analysis, and itappeared to engage a tyrosine kinase receptor distinct from the insulinreceptor.

These insulin-like hormones are expected to subserve the longevity,dauer arrest, and/or metabolic effects of DAF-2 signaling. For example,each of these insulin superfamily members are expected to engage theDAF-2 receptor, leading to a result in which a mutation in daf-2 “sums”the functions of these eight or more insulin-like signals.

An analysis of the F13B12 insulin-like hormone is consistent with thisview (Tables II–VI). First, as shown below, increasing the dose of theF13B12 insulin-like hormone potently modulates dauer arrest, both inanimals carrying weak daf-2 or weak daf-7 mutations, and in animalscarrying defects in synaptic components likely to mediate insulinrelease in C. elegans (unc-64).

TABLE II High copy F13B12(ins) enhances the Daf-c phenotype ofdaf-2(e1365) at 20° C. Phenotype of progeny (%) transgenicnon-transgenic Parental non- non- Genotype dauer dauer N dauer dauer NF13B12 transgenic: daf-2(e1365); mgex309 89.0 11.0 163 2.3 97.7 213daf-2(e1365); mgex310 90.5 9.5 220 2.6 97.4 115 Control trangenic:daf-2(e1365); mgex315 1.8 98.2 283 0.5 99.5 184

TABLE III High copy F13B12(ins) maternally suppresses the Daf-cphenotype of daf-7(e1372) at 25° C. Phentype of progeny (%)non-transgenic (but transgenic parent was) Parental non- non- Genotypedauer dauer N dauer dauer N F13B12 trangenic: daf-7(e1372); mgex299 31.468.6 236 2.9 97.1 172 daf-7(e1372); mgex301 16.8 83.2 250 0 100 122Control transgenic: daf-7(e1372); mgex312 100 0 78 100 0 60

TABLE IV High copy F13B12(ins) maternally suppresses the Daf-c phenotypeof daf-7(e1372) at 15° C. Phenotype of progeny (%) non-trangenic (buttransgenic parent was) Parental non- non- Genotype dauer dauer N dauerdauer N F13B12 transgenic: daf-7(e1372); mgex299 1.4 98.6 73 0.3 99.7343 daf-7(e1372); mgex301 0.5 99.5 194 0 100 278 Control trangenic:daf-7(e1372); mgex312 26.4 73.6 91 25.6 74.4 39

TABLE V High copy F13B12(ins) promotes recovery of unc-64(e246) dauersat 27° C. Phenotype of progeny (%) Day 3 Day 2 Trangenic Non-transgenicParental Non- Non- Non- Genotype Dauer dauer Dauer dauer Dauer dauer NF13B12(ins) transgenic: unc-64(e246); mgex299 91.0 9.0 10.4 56.6 23.69.4 106 unc-64(e246); mgex301 75.3 24.7 22.9 51.1 18.7 7.3 96 Controltransgenic: unc-64(e246); mgex3312 88.9 11.1 54.3 10.6 29.8 5.3 208

TABLE VI High copy F13B12(ins) enhances the Daf-c phenotype ofunc-64(e246) at 15° C. Phenotype of progeny (%) transgenicnon-transgenic Parental non- non- Genotype dauer dauer N dauer dauer NF13B12 transgenic: unc-64(e246); mgex299 23.2 76.8 185 0 100 170unc-64(e246); mgex301 36.0 64.0 75 0 100 77 Control trangenic:unc-64(e246); mgex312 0 100 177 0 100 134A genetic analysis has shown that high F13B12 insulin-like hormonesignaling can suppress dauer arrest induced by daf-7 mutations ordecreases in synaptic signaling, but can enhance dauer arrest caused bydecreases in daf-2 signaling. Thus, the F13B12 insulin-like hormone mayact synergistically with DAF-7 signals, like the DAF-2 receptor, but mayinterfere with the secretion or activity of another DAF-2 ligand. Thesegenetic data strongly implicate the F13B12 insulin-like hormone in DAF-2signaling.

In addition, the expression pattern of a promoter fusion of the F13B12insulin-like hormone to GFP is also consistent with the genetic results.In these experiments, GFP was expressed in several head neurons,including ASJ and ASH, a pair of pharyngeal neurons, with processes thatlooked most like NSM, and three tail neurons. The full-length GFP lookedsimilar but very faint. Worms expressing the full-length GFP livedlonger than wild type. Interestingly, the NSM neuron had dense corevesicles by EM analysis, which is also true of beta cells of thepancreas. Pancreatic beta cells are also neuronal in character; they usesynaptic components for insulin vesicle release, are synapticallyconnected to the autonomic nervous system, and are electrically active.Sulfonyl ureas, which are used to increase insulin release, act byregulating the activity of K channels in beta cells, much the way Kchannels regulate excitability in other neurons. Finally, the NSM neuronis a part of the C. elegans enteric nervous system, just like thepancreas in mammals. Accordingly, the expression and functional analysisof the F13B12 insulin-like hormone is highly supportive of its role ininsulin-like control of worm metabolism and aging.

Although the F13B12 insulin-like hormone is the closest C. eleganshomologue to insulin, it is likely that many or all of these insulinsuperfamily members engage the DAF-2 receptor to regulate theiractivity. For example, they are more closely related to insulin than tothe ligands of the other growth factor receptors present in the wormgenome. These distinct insulin superfamily ligands could regulate DAF-2at distinct times or places, or act antagonistically or synergisticallyto the F13B12 insulin-like hormone. Some of these insulin-like hormonesmay regulate metabolism, like insulin, whereas others may regulate dauerarrest or longevity. Thus, the daf-2 mutant phenotype that results fromloss of the receptor for these many hormones may be a composite loss ofmany hormonal signals. Consistent with such a model, neuronal expressionof the DAF-2 receptor in a daf-2 null mutant has been found tocomplement the dauer arrest phenotype of a daf-2 mutant but not themetabolic or aging defects. Accordingly, one DAF-2 ligand may beexpressed in or near the brain to control dauer arrest, but otherligands may impinge on DAF-2, for example, in non-neuronal cells, tocontrol metabolism and aging.

By this view, loss of only one of the insulin-like hormones may causeonly a subset of the daf-2 mutant phenotype, for example, only increasedlongevity or only metabolic dysregulation. These C. elegans insulinsuperfamily members may, for example, subserve the longevity orsenescence function of DAF-2 receptor signaling, and an increase in sucha hormone activity late in life may actually mediate the increase inDAF-2 activity that causes senescence. Conversely, if any of theseinsulin-like proteins have antagonistic effects on DAF-2, any decline intheir activity late in life could mediate senescence. Application ofonly one hormone by injection or germ line therapy could therefore beused to target, for example, aging without any effects on metabolism.

In addition, since the F13B12 insulin-like hormone is a detectable wormhomologue of insulin, it is possible that the other 7 worm insulins alsohave human homologues that are more closely related to their nematodecounterparts than they are to each other. In fact the divergence of theF13B12 insulin-like hormone from insulin and IGF-I and IGF-II gives ameasure of how much divergence may be expected for the mammalianhomologues of the other insulin superfamily members. The F13B12insulin-like hormone is slightly more closely related to IGF-II thaninsulin or IGF-I, but these three genes are probably duplicated anddiverged homologues of a F13B12 homologue in the common ancestor of C.elegans and Homo sapiens. In fact, it is a current rule of thumb thatmany gene families in mammals have 4 times as many members as in C.elegans. For example, there are 4 Hox clusters in mammals and only onein C. elegans. Similarly, there are 3 known DAF-2 receptor homologuesand DAF-16 transcription factor homologues in mammals (it is likely thatthe fourth mammalian member of these gene families will become knownwhen the full mammalian genome sequence is finished). Thus, it isreasonable to expect that, for every insulin like protein in C. elegans,there may be four in mammals, or a total of 24 for the family of 8 shownabove. In addition, since the F13B12 insulin-like hormone is expressedin only a few neurons, it is possible that the other insulin superfamilymembers are similarly expressed in a small set of neurons, and that thehuman homologues may be expressed in only rare regulatory cell types.

The insulin-like hormones described herein, as well as their humanhomologues, provide valuable candidate regulators of senescence. Forexample, if human senescence is triggered by a decline in aninsulin-like longevity hormone, in analogy to how puberty is triggeredby a timed change in sexual maturation hormones, it may prove possibleto regulate the aging process in the same way that sexual maturation canbe regulated by hormone treatment. In addition, the C. elegans aginghormones may reveal which human genes have such a function. Becausedaf-2 mutations cause longevity increases in a manner analogous tocaloric restriction in mammals, it is possible that caloric restrictionin mammals regulates the level of an insulin-like hormone that in turnengages the insulin or IGF-I, II receptors. Such a hormone may not havebeen detected if its level is very low or if it signals over a shortrange. However, once the human genome sequence is complete, thedetection of human homologues to the C. elegans superfamily memberslisted above will become a trivial matter of database searching. In thisway, the determination of the function of the worm homologue function inlongevity or growth arrest or metabolism control will supply valuablefunctional information about the activity of human homologues.

The effect of the C. elegans insulin-like proteins on longevity,metabolism, or growth arrest may be readily determined by a combinationof high copy studies, as shown above for the F13B12 insulin-likehormone, as well as by using RNA inhibition and knockout strategies toinhibit the activities of these genes. The C. elegans strains are thentested for interactions with dafpathway mutants, for example, as shownfor the F13B12 insulin-like hormone above, and for longevity effects bystandard techniques.

The human proteins that regulate longevity may be detected by acombination of database searches and genetic complementation of wormRNAi or gene knockout mutants (for example, as described herein), aswell as by high copy effects of human genes on worm longevity andmetabolic control.

Because these human proteins are hormones, they may be used to directlyregulate human longevity, for example, by injection into thebloodstream. Depending on the particular hormone and its effects, thehormones themselves may cause increased longevity, or they may bemodified to generate dominant interfering hormones (for example, byengineering chimeras between the insulin superfamily members). Thefunction of these proteins upon injection into the bloodstream may bepredicted from their function in C. elegans, for example, as ascertainedby transgenic analysis. Because of their effects on longevity, the humanhomologues of these C. elegans insulin-like endocrine signals haveimportant applications in preventing or retarding the aging process.

C. elegans Akt/PKB Transduces Insulin Receptor-like Signals from AGE-1Phosphoinositide-3-OH Kinase to the DAF-16 Transcription Factor

An insulin receptor-like signaling pathway regulates C. elegansmetabolism, development, and longevity (Kimura et al., Science277:942–946, 1997). In response to a secreted pheromone, wild typeanimals arrest development at the dauer stage with a concomitant switchto fat storage metabolism in the intestine and hypodermis, increasedlifespan, and remodelling of many tissues (Kimura et al., Science277:942–946, 1997; Riddle and Albert, in C. elegans II, eds. Riddle, D.L., Blumenthal, T., Meyer, B. J. & Priess, J. R., Cold Spring HarborLaboratory Press, Cold Spring Harbor, N.Y., pp. 739–768, 1997).Mutations in the insulin/IGF-I receptor homolog daf-2 (Kimura et al.,Science 277:942–946, 1997) or in the phosphoinositide-3-OH kinase (PI3K)homolog age-1 (Morris et al., Nature 382:536–539, 1996) causeconstitutive arrest at the dauer stage; genetic analysis is consistentwith AGE-1 functioning downstream of DAF-2 (Gottlieb and Ruvkun,Genetics 137:107–120, 1994; Larsen et al., Genetics 139:1567–1583,1995). Mutations in the Fork head transcription factor DAF-16 completelysuppress the dauer arrest, metabolic shift, and longevity phenotypes ofdaf-2 and age-1 mutants (Gottlieb and Ruvkun, Genetics 137:107–120,1994; Larsen et al., Genetics 139:1567–1583, 1995; Kenyon et al., Nature366:461–464, 1993; Ogg et al., Nature 389:994–999, 1997; Lin et al.,Science 278:1319–1322, 1997), indicating that DAF-16 is a negativelyregulated downstream target of C. elegans insulin receptor signaling.Molecules that couple the DAF-2 insulin receptor protein and AGE-1 PI3Kto the DAF-16 transcription factor have not been identified by previousextensive genetic screens. While biochemical studies have suggested thatthe mammalian Akt/PKB (also known as RAC) serine/threonine kinase maytransduce signals from PI3Ks associated with receptor tyrosine kinases(Franke et al., Cell 81:727–736, 1995; Burgering and Coffer, Nature376:599–602, 1995; Cross et al., Nature 378:785–589, 1995), such as theinsulin receptor to downstream effectors, this has not been demonstratedby genetic analysis of signaling pathways in whole organisms. Weestablished the action of C. elegans Akt/PKB in the DAF-2 insulinreceptor-like signaling pathway by the genetic identification of anactivating Akt/PKB mutation and by genetic analysis of Akt/PKBinactivation and overexpression.

An activating mutation (mg144) in akt-1, one of two C. elegans Akt/PKBhomologs, was identified in a genetic screen for mutations that suppressthe dauer arrest phenotype of the age-1(mg44) null mutant (Morris etal., Nature 382:536–539, 1996). This screen was designed to isolatereduction of function mutations in molecules negatively regulated byPI3K signaling, or gain of function mutations in molecules positivelyregulated by PI3K signaling. Among 10 independent suppressor mutationsisolated in a screen of 3800 haploid genomes, in addition to theactivating akt-1 mutation, we also isolated multiple alleles of apreviously known negatively regulated target, daf-16 (Gottlieb andRuvkun, Genetics 137:107–120, 1994; Larsen et al., Genetics139:1567–1583, 1995) and one other suppressor that maps to the daf-16interval between lin-11 and unc-75, suggesting that the screen revealedgenes that act in this insulin-like signaling pathway. Another dominantmutation, mg142, that suppresses multiple age-1 alleles and sixmutations that vary in their ability to suppress multiple age-1 alleleswere also isolated in the screen.

The mg144 mutation suppresses the three age-1 alleles tested, includingtwo classes of nonsense alleles and one missense substitution(Ala845Thr) in a conserved region of PI3K (Morris et al., Nature382:536–539, 1996). mg144 is completely dominant for suppression of thedauer constitutive phenotype of age-1(mg44) (75.1% of the progeny ofage-1(mg44); mg144/+ animals developed as non-dauers, and 24.9% arrestedat the dauer stage, N=774). On its own, mg144 does not have any obviousphentoypes; it moves normally, has a normal vulva and brood size, andmakes dauers on starved plates and on plates treated with pheromone.Thus mg144 does not activate the AGE-1 PI3K signaling pathway to thepoint that normal dauer arrest is affected but does activate the pathwaysufficiently to alleviate the requirement for AGE-1 PI3K outputs.

Using suppression of the dauer constitutive phenotype of age-1(mg44),mg144 was mapped to a region on chromosome V within 1.3 mu of thepolymorphic STS marker bP1 (FIG. 31). From the C. elegans genomesequence in this 1.3 mu region, we identified a C. elegans Akt/PKBhomolog which we named akt-1 (FIG. 31). Because an activating mutationin Akt/PKB is a good candidate to be a genetically dominant suppressorof an age-1 PI3K null mutant, we determined the akt-1 DNA sequence inthe mg144 strain by PCR amplification and direct sequencing. The akt-1gene in the mg144 mutant strain was shown to bear an Ala183Thrsubstitution (FIG. 34). akt-1 is differentially spliced within theconserved kinase domain to generate the akt-1a and akt-1b isoforms withdistinct kinase domain subregions IV, V, and VI (92% identical, 238/258amino acids over the entire kinase domain; 69% identical, 44/64 aminoacids in the differentially spliced region). akt-1a is 58% identical tohuman Akt/PKBa (FIGS. 33 and 34). akt-1 has a pleckstrin homologydomain, kinase domain, and the two phosphorylation sites necessary forAkt/PKB activation (Alessi et al., EMBO J. 15:6541–6551, 1996) which arethe hallmarks of the Akt/PKB family (FIG. 34). The next most closelyrelated non-Akt/PKB mammalian kinase is rat PKCβ1 which is 38% identicalto akt-1a. The akt-1(mg144) mutation is present in both splice forms ofakt-1 and is located in a region of the protein that links theN-terminal pleckstrin homology domain to the C-terminal kinase domain.This mutation is in a region that is not conserved between C. elegansand mammalian Akt/PKB. This mutation may reveal a negative regulatoryregion on akt-1 because the mg144 allele is an activating mutation (seebelow).

To confirm that the mg144 suppression of age-1 that is geneticallylinked to akt-1 was due to a mutation in akt-1, we used a reversegenetic assay termed RNA interference (RNAi) (Fire et al., Nature391:806–811, 1998; Rocheleau et al., Cell 90:707–716, 1997; Zhang etal., Nature 390:477–484, 1997) to decrease akt-1 gene activity in anage-1(mg44); akt-1(mg144) strain. If a mutation in akt-1 was responsiblefor the suppression of age-1 observed in this strain, RNAi of akt-1 inthis strain should revert the suppression phenotype and result in adauer constitutive phenotype. This experiment was conceptually similarto the classic genetic arguments that show that a cis-acting loss offunction mutation can revert a gain of function mutation in the samegene. Inhibition of akt-1 activity in an age-1(mg44); akt-1(mg144)strain reverted the akt-1(mg144) suppression phenotype, indicating thatthe mg144 activating mutation was a lesion in the akt-1 locus.

We identified another Akt/PKB homolog in the nearly complete C. elegansgenome sequence (Wilson et al., Nature 368:32–38, 1994) which we namedakt-2 (FIG. 32). akt-1 and akt-2 are more closely related to each other(66% identity between akt-1a and akt-2 overall) than to any otherAkt/PKB homolog (FIG. 33). akt-2 is 55% identical to human Akt/PKBaoverall and 35% identical to rat PKCβ1 overall. Interestingly, akt-2only has the Thr308 phosphorylation site that is necessary for Akt/PKBactivation by PDK1 (Alessi et al., Current Biology 7:261–269, 1997;Stokoe et al., Science 277:567–570, 1997) but not the Ser473phosphorlyation site (Alessi et al., EMBO J. 15:6541–6551, 1996) (FIG.34) and yet clearly functions in the insulin-like signaling pathway (seebelow).

Reduction of both akt-1 and akt-2 activities revealed that theytransduce insulin-like signals from the AGE-1 PI3K to the DAF-16forkhead transcription factor. Inhibition of either akt-1 or akt-2activity by RNAi did not cause dauer arrest. However, simultaneousinhibition of both akt-1 and akt-2 activities caused nearly 100% arrestat the dauer stage. We concluded that Akt/PKB signaling from eitherakt-1 or akt-2 is sufficient for reproductive development. This resultindicates that akt-1 and akt-2 can function redundantly for dauerformation in C. elegans and raises the possibility that variousmammalian Akt/PKB isoforms could function redundantly as well.Significantly, the constitutive dauer arrest induced by inhibition ofboth akt-1 and akt-2 is fully suppressed by a null mutation in daf-16(Ogg et al., Nature 389:994–999, 1997) but is not suppressed by a nullmutation in the Smad homolog daf-3 (Patterson et al., Genes &Development 11:2679–2690, 1997) which confirms its placement in theDAF-2/AGE-1/DAF-16 signaling pathway. Because a null mutation in daf-16alleviates the need for C. elegans Akt/PKB signaling, the primaryfunction of AKT-1 and AKT-2 is to antagonize DAF-16. Interestingly,DAF-16 contains four consensus sites for phosphorylation by Akt/PKB(Alessi et al., FEBS Letters 399:333–338, 1996) and three of these sitesare conserved in the human DAF-16 homologs AFX, FKHR, and FKHRL1. AKT-1and AKT-2 may exert their negative regulatory effect by directlyphosphorylating DAF-16. Shown below are comparisons of AFX, FKHR, andDAF-16, indicating the conservation between the consensusphosphorylation sites. The AKT sites indicated are located downstreamand upstream, respectively, of the Forkhead domain (SEQ ID NOS:161–169).

Score = 151 (68.4 bits), Expect = 1.9e−140, Sum P (8) = 1.9e−140Identities = 28/54 (51%), Positives = 38/54 (70%) AFX: 226SPVGHFAKWSGSPCSRNREEADMWTTFRPRSSSNASSVSTRLSPLRPESEVLAE 279SP   F+KW  SP S + ++ D W+TFRPR+SSNAS++S RLSP+  E + L E FKHR: 287SPGSQFSKWPASPGSHSNDDFDNWSTFNASTISGRLSPIMTEQDDLGE 340 DAF-16a                         SFRPRTQSNLSIPGSSS                           ▬▬▬▬▬▬                            ▬▬▬▬▬▬Score = 132 (59.8 bits), Expect = 1.9e−140, Sum P (8) = 1.9e−140Identities = 22/42 (52%), Positives = 28/42 (66%) AFX: 7KAAAIIDLDPDFEPQSRPRSCTWPLPRPEIANQPSEPPEVEP 48+A  ++++DPDFEP  RPRSCTWPLPRPE +   S      P FKHR: 3EAPQVVEIDPDFEPLPRPRSCTWPLPRPEFSQSNSATSSPAP 44 DAF-16TFMNTPDDVMMNDDMEPIPRDRCNTWPMRRPQLEPPLNSSP 177T  ++P+ V ++ D EP+PR R  TWP+ RP++  + ++++

We have shown that human AKT will phosphorylate C. elegans DAF-16 andthat this phosphorylation is dependent on these sites. Upon mutation ofthe serine or threonine in these sites to alanine, in vitrophosphorylation of DAF-16 (or fragments of DAF-16) is abolished. It isexpected that the lack of akt input to DAF-16 in these mutant nematodeswill result in dauer arrest, just like animals lacking akt-1/akt-2 geneactivity.

The above genetic results show that Akt/PKB is the major output of PI3Ksignaling and implicate a transcription factor downstream target for theAkt/PKB kinase. Because mutations in daf-16 suppress akt-1 and akt-2reduction of function, it is likely that DAF-16 represents a majorsignaling output of Akt/PKB in C. elegans insulin-like signaling.Akt/PKB has been implicated in mammalian insulin receptor signaling thatlocalizes glucose transporters to the plasma membrane (Kohn et al., J.Biol. Chem. 271:31372–31378, 1996) and has been shown to regulateglycogen synthesis via direct phosphorylation of GSK-3 (Cross et al.,Nature 378:785–589, 1995), two events which are not transcriptionallyregulated. While there also may be such Akt/PKB outputs in C. elegans,the DAF-16 Fork head transcription factor represents the major output ofDAF-2/AGE-1/AKT-1/AKT-2 insulin receptor-like signaling (Ogg et al.,Nature 389:994–999, 1997). Similarly Akt/PKB action in the insulin/IGF-Ianti-apoptotic pathway (Dudek et al., Science 275:661–665, 1997;Kauffinann-Zeh et al., Nature 385:544–548, 1997; Kulik et al., Mol. CellBiol. 17:1595–1606, 1997 24–26) may also converge on transcriptionfactors related to DAF-16.

The normal requirement of age-1 activity for reproductive development isalso bypassed by increased gene dosage of wild type akt-1. Transgenicage-1(mg44) animals carrying a 7.3 kb akt-1(+) genomic region can growreproductively rather than arrest at the dauer stage. Greater than 75%of age-1(mg44) animals that contain the akt-1(+) transgene at high copybypass dauer arrest while non-transgenic age-1(mg44) animals neverbypass dauer arrest. This rescue is dependent on a conserved lysineresidue implicated in mammalian AKT/PKB kinase activity (Franke et al.,Cell 81:727, 1995). In a similar experiment with age-1(mg44) animalscarrying the same genomic region amplified from akt-1(mg144) at highcopy, the transgenic animals bypassed dauer arrest at a similarfrequency. The age-1(mg44) animals carrying the akt-1(mg144) transgeneat low copy bypass dauer arrest more frequently than the age-1(mg44)animals carrying the akt-1(+) transgene at low copy (approximately 85%of age-1(mg44) animals carrying akt-1(mg144) transgene bypass dauercompared to 38% of age-1(mg44) animals carrying the akt-1(+) transgene).These results indicate that the same 7.3 kb genomic region amplifiedfrom the akt-1(mg144) strain is a more potent suppressor of age-1(mg44)than the akt-1(+) transgene. These data map mg144 to the 7.3 kb regionof akt-1 that includes the Ala183Thr substitution in AKT-1. However,while multiple independent akt-1 (mg144) transgenes are more potentsuppressors of age-1(mg44) than akt-1(+) transgenes, which suggests thatmore akt-1 gene activity is generated by akt-1(mg144), there issignificant variation in the penetrance of suppression observed withdifferent transgenes. In addition, even though akt-1(+) transgenesconfer suppression of age-1(mg44) that is not observed with chromosomalakt-1(+), the penetrance of suppression of age-1(mg44) by eitherakt-1(+) or akt-1(mg144) transgenes is less than from akt-1(mg144)/+heterozygotes or akt-1(mg144) homozygotes. This may be due to mosaicismof akt-1 gene expression from transgenic arrays or a saturation of akt-1gene function by high gene dosage. These data also suggest that themutation may act by increasing AKT-1 abundance or stability, thusconferring the ability to grow in the absence of age-1 signaling.

Null mutations in age-1 cause dauer arrest as does inactivation of akt-1and akt-2 by RNAi. This indicates that akt-1(+), akt-2(+), and age-1(+)are required for reproductive development. Because the dominant alleleakt-1(mg144) also promotes reproductive growth by virtue of its abilityto suppress the dauer constitutive phenotype of age-1 null mutants, itfunctions similarly to akt-1(+) and akt-2(+). Thus akt-1(mg144) is anactivating mutation, as opposed to a loss of function or dominantnegative mutation in akt-1. In addition, the fact that both akt-1(mg144)and providing additional copies of the akt-1(+) gene suppress an age-1null mutant is consistent with akt-1(mg144) being an activatingmutation.

Because akt-1 and akt-2 function redundantly to repress dauer formationwe asked whether overexpression of akt-2(+) could also bypass the normalrequirement of AGE-1 PI3K signaling. age-1(mg44) animals carrying theakt-2(+) transgene arrested as dauers while age-1(mg44) animals carryingthe akt-1(+) transgene bypassed dauer. Thus, either because ofdifferences in the AKT-2 protein or differences in protein expression,high gene dosage of akt-2 is not able to bypass the usual requirementfor AGE-1 PI3K signaling.

akt-1(mg144) suppresses the dauer constitutive phenotype of three age-1alleles. Because age-1(mg44) is a null mutant, these data stronglysuggest that akt-1 acts downstream of age-1 and demonstrates that thebiochemical ordering of PI3K upstream of Akt/PKB kinase is also true inan intact organism. AGE-1 is the only PI3K homolog in C. elegans of thetype regulated by tyrosine kinase receptors. Significantly, our resultsdemonstrate that C. elegans Akt/PKB gene activity is not strictlydependent on upstream age-1 activity if Akt/PKB activity is increasedbecause akt-1(mg144) as well as akt-1(+) overexpression suppress nullmutations in AGE-1 PI3K. This is comparable to the suppression bydaf-16(m27), a reduction of function allele (Lin et al., Science278:1319–1322, 1997), and daf-16 null alleles (Ogg et al., Nature389:994–999, 1997).

A mutation in daf-2 is suppressed more poorly by akt-1(mg144) than by areduction of function mutation in daf-16. The age-1 alleles suppressedby akt-1(mg144) are null (Morris et al., Nature 382:536–539, 1996)whereas daf-2(e1370) is a temperature sensitive mutation in the kinasedomain (Kimura et al., Science 277:942–946, 1997). This daf-2 allele iscompletely suppressed by many daf-16 alleles, including null alleles(Gottlieb and Ruvkun, Genetics 137:107–120, 1994; Larsen et al.,Genetics 139:1567–1583, 1995; Ogg et al., Nature 389:994–999, 1997).This result, in comparison to the robust suppression of age-1 mutationsby akt-1(mg144), suggests that akt-1 is a major output of AGE-1signaling and one of multiple outputs of DAF-2 signaling. In addition,because akt-1(mg144) can bypass the need for AGE-1 PI3K signaling butnot for DAF-2 insulin receptor-like signaling, akt-1(mg144) defines abifurcation in the signaling pathway downstream of daf-2. It is likelythat age-1 and akt-1 constitute one major signaling pathway from DAF-2and that other, as yet unidentified genes, constitute one or moreparallel pathways. These pathways converge downstream of AGE-1 and at orupstream of the DAF-16 Fork head transcription factor and negativelyregulate its activity, since loss of function mutations in daf-16completely suppress both daf-2 and age-1 mutations (Gottlieb and Ruvkun,Genetics 137:107–120, 1994). Because a decline in AGE-1 PI3K orAKT-1/AKT-2 signaling induces dauer arrest in the presence of signalingfrom this parallel pathway, both are necessary for reproductivedevelopment. The genetic evidence for multiple DAF-2 insulinreceptor-like outputs demonstrate that biochemical studies showing thatparallel PI3K, ras, SHP2, and other signaling outputs are activated bythe insulin receptor in mammals (Kahn, Diabetes 43:1066–1084, 1994) arerelevant to insulin receptor-like signaling in intact organisms.

In addition, a mutation in daf-2 is suppressed more poorly byakt-1(mg144) than by a reduction of function mutation in daf-16. Theage-1 alleles suppressed by akt-1(mg144) are null (Morris et al. (1996)Nature 382:536–539) whereas daf-2(e1370) is a temperature sensitivemutation in the kinase domain (Kimura et al. (1997) Science277:942–946). This daf-2 allele is completely suppressed by many daf-16alleles, including null alleles (Gottlieb and Ruvkun (1994) Genetics137:107–120; Larsen et al. (1995) Genetics 139:1567–1583; Ogg et al.(1997) Nature 389:994–999). This result, in comparison to the robustsuppression of age-1 mutations by akt-1 (mg144), suggests that AKT-1 isa major output of AGE-1 signaling and one of multiple outputs of DAF-2signaling.

Overexpression of either akt-1(+) or akt-1(mg144) can bypass the needfor DAF-2 signaling while overexpression of akt-2(+) or akt-1(KD) doesnot alleviate the need for DAF-2 signaling. However, akt-1(+) andakt-1(mg144) transgenes are more efficient suppressors of the dauerconstitutive phenotype of age-1(mg44) than of daf-2(e1370). Thissupports the model that AKT-1 is a primary output of AGE-1 signaling butnot DAF-2 signaling.

Reduction of zygotic age-1 activity increases C. elegans lifespangreater than two-fold (Morris et al., Nature 382:536–539, 1996; Larsenet al., Genetics 139:1567–1583, 1995; Klass, Mech. Ageing Dev.22:279–286, 1983). Mutations in daf-16 suppress this lifespan increase(Larsen et al., Genetics 139:1567–1583, 1995; Dorman et al., Genetics141:1399–1406, 1995). akt-1(mg144) does not suppress the age-1(mg44)induced increase in lifespan (for the following strains, mean lifespans,maximum lifespan are given: N2 12 days, 16 days, N=28; sqt-1(sc13)age-1(mg44) 18 days, 36 days, N=20; sqt-1(sc13) age-1(mg44);akt-1(mg144) 22 days, 38 days, N=36; daf-16(m27); sqt-1(sc13)age-1(mg44) 14 days, 16 days, N=32). Thus akt-1(mg144) bypasses the needfor AGE-1 signaling in reproductive development but does not activatenormal aging pathways. It is possible that akt-1(mg144) does notsubserve all the functions of the wild type akt-1 or akt-2. akt-2 orother as yet unidentified downstream effectors of age-1 may be thepertinent signaling molecules for lifespan regulation.

The expression patterns of both akt-1 and akt-2 were examined intransgenic animals containing a translational fusion of each genomiclocus to Green Fluorescent Protein (GFP) (Chalfie et al., Science263:802–805, 1994). The GFP fusion proteins contain the entire genomiccoding region from either akt-1 or akt-2, including 5′ upstreamregulatory sequence, fused in frame at the C-terminus to GFP. TheAKT-1/GFP construct is sufficient to suppress the dauer constitutivephenotype of age-1(mg44) while the AKT-2/GFP construct is not. Thisresult is not unexpected because increased gene dosage of akt-2(+) doesnot suppress age-1(mg44) while increased gene dosage of akt-1(+) does.AKT-1/GFP expression is first observed in late embryos and is maintainedthroughout the life of the animal. In post-embryonic animals, AKT-1/GFPis expressed in the majority of head neurons including sensory neurons.Expression is also observed in motor neurons of the ventral and dorsalnerve cord, neuronal commissures and processes throughout the body, andthe tail neurons. The fusion protein is localized throughout the cellbody and axonal and dendritic processes of neurons but is usuallyexcluded from the nucleus. Additional tissues which consistently expressAKT-1/GFP include neurons and muscle cells of the pharynx, the rectalgland cells, and the spermatheca. AKT-1/GFP expression was observed morevariably in a variety of cell types including hypodermis, intestine,muscle, some of the P cell descendants that form the vulva, and in theexcretory canal.

Consistent with redundant roles of akt-1 and akt-2, an AKT-2/GFP fulllength protein fusion gene is expressed at the same times as AKT-1/GFPand in the same tissues that express AKT-1/GFP, although AKT-2/GFP seemsto be less abundant. In dauers induced by starvation on crowded plates,AKT-1/GFP and AKT-2/GFP expression does not differ dramatically fromtheir expression during reproductive growth. These expression patternsare consistent with AKT-1 and AKT-2 functioning either in secretoryneurons to regulate dauer arrest and metabolic shift or in the targettissues that are remodeled during dauer formation such as the pharynx,hypodermis, and intestine.

The activating mutation akt-1(mg144), as well as overexpression ofakt-1(+), bypasses the normal requirement for AGE-1 PI3K signaling inthe DAF-2 insulin receptor-like signal transduction pathway. Theseresults demonstrate that C. elegans Akt/PKB gene activity is notstrictly dependent on upstream age-1 activity if Akt/PKB activity isincreased. In the almost complete C. elegans genome sequence, AGE-1 isthe only PI3K homolog of the type known to generate 3-phosphoinositides.If AGE-1 is the only protein able to generate 3-phosphoinositides in C.elegans, these results suggest that, while normal AKT-1 signaling isdependent on 3-phosphoinositides, AKT-1 can become activated in theirabsence if gene dosage is increased or the mg144 mutation is introduced.

Importantly, either activated akt-1 or higher akt-1(+) gene dosage doesnot efficiently suppress mutations in the DAF-2 insulin receptorsuggesting that age-1 and akt-1 constitute one major signaling pathwayfrom DAF-2 and that other, as yet unidentified genes, constitute one ormore parallel pathways. These pathways most likely converge on theDAF-16 Fork head transcription factor and negatively regulate itsactivity, since loss of function mutations in daf-16 completely suppressboth daf-2 and age-1 mutations (Gottlieb and Ruvkun (1994) Genetics137:107–120; Larsen et al. (1995) Genetics 139:1567–1583), as well asinactivation of akt-1 and akt-2 signaling.

While AKT-1 and AKT-2 appear to function redundantly in transduction ofDAF-2/AGE-1 signals, increased akt-1 gene dosage is a much more potentsuppressor of age-1 null mutations than increased akt-2 gene dosage. Amajor distinction between AKT-1 and AKT-2 is that AKT-1 bears twodistinct phosphorylation sites (corresponding to Thr308 and Ser473 inhuman Akt/PKBa) that are necessary for activation of Akt/PKB by upstreamgrowth factor inputs (Alessi et al. (1996) EMBO J. 15:6541–6551; Alessiet al. (1996) FEBS Letters 399:333–338) while AKT-2 only has the Thr308phosphorylation site. In mammals, Akt/PKB is phosphorylated at Thr308 byPDK1 and at Ser473 by the as yet unpurified PDK2 (Alessi et al. (1997)Current Biology 7:261–269; Stokoe et al. (1997) Science 277:567–570).Thus AKT-1 may couple to a PDK2-like kinase whereas AKT-2 cannot do so.AKT-1 and AKT-2 may also differ in other kinase inputs or in theirsubstrates. Interestingly, at lower temperatures, the akt-2(+) transgenecan supply sufficient Akt/PKB activity to weakly suppress the dauerarrest caused by age-1(mg44). Temperature is a major modulator of dauerarrest (Riddle and Albert (1997) Genetic and Environmental Regulation ofDauer Larva Development. In C. elegans II (ed. D. L. Riddle, T.Blumenthal, B. J. Meyer and J. R. Priess), pp. 739–768, Cold SpringHarbor Laboratory Press, Cold Spring Harbor, N.Y.). The penetrance ofdauer arrest in most dauer constitutive mutants is increased at hightemperatures (Riddle and Albert (1997) Genetic and EnvironmentalRegulation of Dauer Larva Development. In C. elegans II (ed. D. L.Riddle, T. Blumenthal, B. J. Meyer and J. R. Priess), pp. 739–768, ColdSpring Harbor Laboratory Press, Cold Spring Harbor, N.Y.), suggestingthat some signals in the pathway are enhanced at low temperature. Thusat low temperatures perhaps PDK1 signaling to AKT-1 and AKT-2 orsignaling in pathways parallel to AGE-1/AKT-1/AKT-2 are enhanced,allowing increased akt-2(+) gene dosage to weakly bypass the normalrequirement for AGE-1 PI3K signaling.

Insulin-like and TGF-β neuroendocrine signals regulate whether animalsarrest at the dauer stage or grow to reproductive adults (Kimura et al.(1997) Science 277:942–946; Riddle and Albert (1997) Genetic andEnvironmental Regulation of Dauer Larva Development. In C. elegans II(ed. D. L. Riddle, T. Blumenthal, B. J. Meyer and J. R. Priess), pp.739–768, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y.).The TGF-β-like molecule DAF-7 is a probable neuroendocrine signal: it isexpressed in the sensory neuron ASI that represses dauer arrest(Bargmann and Horvitz (1991) Science 251:1243–1246) and its expressionis regulated by dauer-inducing pheromone (Ren et al. (1996) Science274:1389–1392; Schackwitz et al. (1996) Neuron 17:719–728). While theinsulin-like ligand for the DAF-2 insulin-like receptor has not yet beenidentified, it may also be produced by secretory neurons and regulatedby pheromone. Precedent from biochemical analysis predicts that DAF-2,AGE-1, AKT-1/AKT-2, and DAF-16 function in the same cells. It is not yetclear whether the DAF-2 signaling pathway acts in the target tissuesthat are remodeled in dauer larvae such as the pharynx, hypodermis, andintestine, or in other signaling cells that in turn control targettissues. The broad expression pattern of akt-1 and akt-2 includes thenervous system, pharynx, and hypodermis. This expression pattern isconsistent with a role for these genes either in sensory neurons thatsignal to repress dauer arrest or in the target tissues that receive thedauer repressing signal. The expression patterns of daf-2 and age-1 havenot been reported; daf-16 is widely expressed (Ogg et al. (1997) Nature389:994–999) as are daf-3 and daf-4, two genes that comprise the DAF-7TGF-β signal reception pathway (Patterson et al. (1997) Genes andDevelopment 11:2679–2690). Mosaic or tissue-specific expression analysiswill be required to demonstrate in which cell types the DAF-2insulin-like and DAF-1/DAF-4 TGF-β signal transduction pathways act.

The role of AKT-1 and AKT-2 in regulating the metabolic shift anddevelopmental arrest associated with dauer formation suggests thefollowing model. Under normal growth conditions, an insulin-likemolecule binds to the DAF-2 insulin receptor kinase inducingautophosphorylation and recruitment of AGE-1 PI3K. As discussed herein,PI3K signals via Akt/PKB. Precedent from biochemical experiments inother systems (Franke et al., Cell 81:727–736, 1995; Franke et al.,Science 275:665–668, 1997; Klippel et al., Mol. Cell Biol. 17:338–344,1997) suggests that AGE-1 activation produces phospholipids that bind toand activate AKT-1 and AKT-2 by inducing a conformational change in theprotein that makes it accessible to phosphorylation events which arenecessary for activation (Alessi et al., Current Biology 7:261–269,1997; Stokoe et al., Science 277:567–570, 1997). A parallel pathway orpathways from the DAF-2 insulin receptor-like protein is also activated.The AKT-1 and AKT-2 kinases, as well as molecules from the parallelpathway, negatively regulate DAF-16 activity, possibly viaphosphorylation. Phosphorylated DAF-16 could be inactive, function toactivate genes required for reproductive growth and metabolism, orrepress genes required for dauer arrest and energy storage. Othersignaling molecules that are activated by DAF-2 must also convergedownstream of AGE-1 (for example, on DAF-16 or AKT-1/AKT-2) for properregulation of metabolism and lifespan: the dauer arrest induced by lossof AGE-1 PI3K or AKT-1/AKT-1 activity implies that the loss of only oneof these inputs to DAF-16 is sufficient to cause dauer arrest. Underdauer inducing conditions, DAF-2, AGE-1, AKT-1/AKT-2, and othersignaling pathways from DAF-2 are inactive and therefore DAF-16 isactive, presumably because it is under-phosphorylated. Active DAF-16either represses genes required for reproductive growth and metabolismor activates genes necessary for dauer arrest and energy storage.

The DAF-16 Fork head protein has been suggested to interact with theDAF-3, DAF-8, or DAF-14 Smad proteins to integrate converging TGF-β likeneuroendocrine signals with insulin-like signals (Ogg et al., Nature389:994–999, 1997; Patterson et al., Genes & Development 11:2679–2690,1997). DAF-16 may form a complex with the DAF-3 Smad protein under dauerinducing conditions to regulate these downstream genes (Ogg et al.,Nature 389:994–999, 1997), while AKT-1 phosphorylation of DAF-16 mayinhibit the formation of a Smad/Fork head complex during reproductivedevelopment.

Akt/PKB has been implicated in mammalian insulin receptor signaling thatlocalizes glucose transporters to the plasma membrane (Kohn et al.(1996) J. Biol. Chem. 271:31372–31378) and has been shown to regulateglycogen synthesis via direct phosphorylation of GSK3 (Cross et al.(1995) Nature 378:785–789); two events that are not transcriptionallyregulated. While there also may be such Akt/PKB outputs in C. elegans,the DAF-16 Fork head transcription factor represents the major output ofDAF-2/AGE-1/AKT-1/AKT-2 insulin receptor-like signaling (Ogg et al.(1997) Nature 389:994–999). Similarly Akt/PKB action in theinsulin/IGF-I anti-apoptotic pathway (Dudek et al. (1997) Science275:661–665; Kauffinann-Zeh et al. (1997) Nature 385:544–548; Kulik etal. (1997) Mol. Cell Biol. 17:1595–1606) may also converge ontranscription factors related to DAF-16.

The present model, based on genetic evidence that Akt/PKB couplesinsulin receptor-like signaling to transcriptional output via the DAF-16Fork head transcription factor in C. elegans, predicts that Akt/PKB willhave transcriptional outputs in insulin-like signaling across phylogeny.It was previously suggested that the human homologs of the DAF-16transcription factor (AFX, FKHR, FKHRL1 and AF6q21) may be the pertinentdownsteam effectors of insulin signaling in humans (Ogg et al., Nature389:994–999, 1997). Two of the consensus Akt/PKB sites conserved inDAF-16 and its human homologs are located outside of the Fork head DNAbinding domain, and two sites are located in the highly basic W2 regionof the Fork head domain that has been shown to mediate DNA phosphatebackbone contacts (Clark et al. (1993) Nature 364:412–420). Insulinstimulated Akt/PKB phosphorylation of the W2 sites may affect DNAbinding whereas the other conserved sites may affect transactivation. Arecent report shows that Akt/PKB mediates insulin dependent repressionof the insulin-like growth factor binding protein-1 (IGFBP-1) gene inHepG2 cells via a conserved insulin response sequence (CAAAAC/TAA) (SEQID NO:318) (Cichy et al., J. Biol. Chem. 273:6482–6487, 1998).Interestingly, we have determined that DAF-16 binds to this same insulinresponse sequence in vitro. We propose that Akt/PKB mediates itstranscriptional effects on insulin responsive genes such as IGFBP-1 viathe human homologs of DAF-16: AFX, FKHR, FKHRL1, or AF6q21.

In addition, genetic analysis suggests that drugs that activate AKT orPDK can bypass the need for AGE-1 PI3K signaling, and mapping ofmutations to particular regions of AKT-1 and PDK-1 points out targetsfor activation of these enzymes. Thus, drugs that activate these kinasesare expected to partially relieve defects in insulin signaling, forexample, associated with type II diabetes. The genetic analysisdescribed herein also suggests that another unknown output of DAF-2insulin like signaling exists. That output may be identified using AKTgain of function mutations to activate the AGE-1 PI3K pathway andscreening for mutations that allow daf-2 receptor mutations to growreproductively. Alternatively, the genes in this parallel pathway may beidentified by screening age-1; daf-18 mutants for arrest at the dauerstage.

PDK Genetics

From the same genetic screen that generated the akt-1(mg144gf) allele,we identified another age-1 suppressor, mg142. This mutation alsobypasses the need for upstream age-1 signaling and is geneticallydominant. Genetic mapping placed the mutation in the region where a C.elegans homologue maps. The genomic sequence of pdk-1, starting 60 bpupstream of the start codon and ending 60 bp downstream of the stopcodon is shown in FIG. 35 (SEQ ID NO: 158). FIGS. 36 and 37 show the twoC. elegans pdk-1 spliced forms, pdk-1a (FIG. 36; SEQ ID NO: 159) andpdk-1b (FIG. 37; SEQ ID NO: 160). The pdk-1(mg142) gain of functionmutation is Ala303Val (splice 1). This protein is 58% identical tomammalian PDK in the plecstrin homology domain and 39% identical in thekinase domain as shown below (SEQ ID NOS:170–202).

Score = 252 (88.7 bits), Expect = 2.2e−60, Sum P (6) = 2.2e−60Identities = 47/80 (58%), Positives = 60/80 (75%), Frame = +3 Query: 439LEKQAGGNPWHQFVENNLILKMGPVDKRKGLFARRRQLLLTEGPHLYYVDPVNKVLKGEI 498LE+Q   NP+H F  N+LILK G ++K++GLFARRR  LLTEGPHL Y+D  N VLKGE+ Sbjct: 1818LEEQRVKNPFHIFTNNSLILKQGYLEKKRGLFARRRMFLLTEGPHLLYIDVPNLVLKGEV 1997 Query:499 PWSQELRPEAKNFKTFFVHT  518 PW+  ++ E KN  TFF+HT Sbjct: 1998PWTPCMQVELKNSGTFFIHT  2057 Score = 201 (70.8 bits), Expect = 2.2e−60,Sum P (6) = 2.2e−60 Identities = 48/123 (39%), Positives = 72/123 (58%),Frame = +1 Query: 263SDLWALGCIIYQLVAGLPPFRAGNEYLIFQKIIKLEYDFPEKFFPKARDLVEKLLVLDAT 322+D+W LGCI++Q +AG PPFRA N+Y + ++I +L++ FPE F  +A +++ K+LV Sbjct: 802TDIWGLGCILFQCLAGQPPFRAVNQYHLLKRIQELDFSFPEGFPEEASEIIAKILV-G*H 978 Query:323 KRLGCE----EMEGYGP--------LKAHPFFESVTWENLHQQTPPKLTAYLPAMSEDDE 370+ L  E     ++   P        L AH FFE+V W N+    PP L AY+PA   + E Sbjct: 979ETLKTEYVIFNLQVRDPSTRITSQELMAHKFFENVDWVNIANIKPPVLHAYIPATFGEPE 1158 Query:371 DCYGN  375   Y N Sbjct: 1159 -YYSN  1170 Score = 180 (63.4 bits),Expect = 2.2e−60, Sum P(6) = 2.2e−60 Identities = 31/72 (43%), Positives= 52/72 (72%), Frame = +2 Query: 157FGLSYAKNGELLKYIRKIGSFDETCTRFYTAEIVSALEYLHGKGIIHRDLKPENILLNED 216F +   +NG+L + +   GSFD   ++F+ +EI++ L++LH   I+HRD+KP+N+L+ +D Sbjct: 287FVIGLVENGDLGESLCHFGSFDMLTSKFFASEILTGLQFLHDNKIVHRDMKPDNVLIQKD 466 Query:217 MHIQITDFGTAK  228  HI ITDFG+A+ Sbjct: 467 GHILITDFGSAQ  502 Score= 83 (29.2 bits), Expect = 2.2e−60, Sum P(6) = 2.2e−60 Identities= 15/53 (28%), Positives = 32/53 (60%), Frame = +2 Query: 108YAIKILEKRHIIKENKVPYVTRERDVMSRLD-----HPFFVKLYFTFQDDEKL 155+A+K+L+K ++ +  K+  + RE+++++ L      HPF  +LY  F D  ++ Sbjct: 8FAVKVLQKSYLNRHQKMDAIIREKNILTYLSQECGGHPFVTQLYTHFHDQARI 166 Score = 81(28.5 bits), Expect = 2.2e−60, Sum P (6) = 2.2e−60 Identities = 15/29(51%), Positives = 19/29 (65%), Frame = +2 Query: 519PNRTYYLMDPSGNAHKWCRKIQEVWRQRY 547 PNR YYL D    A +WC+ I +V R+RY Sbjct:2129 PNRVYYLFDLEKKADEWCKAINDV-RKRY 2212 Score = 78 (27.5 bits), Expect= 2.2e−60, Sum P(6) = 2.2e−60 Identities = 15/25 (60%), Positives= 18/25 (72%), Frame = +3 Query: 232 PESKQARANSFVGTAQYVSPELLTE 256PE   AR  +FVGTA YVSPE+L + Sbjct: 660 PEENTARRTTFVGTALYVSPEMLAD 734

Score = 118 (54.4 bits), Expect = 1.4e−104, Sun F (S) = 1.4e−104Identities = 21/62 (33%), Positives = 41/62 (66%) Query: 63KRTSNDFMFLQSMGEGAYSQVFRCREVATDAMFAVKVLQKSYLNRHQKMDAIIREKNILT 122K+   DF F + +GEG++S V   RE+AT   +A+K+L+K ++ +  K+  + RE+++++ Sbjct: 76KKRPEDFKFGKILGEGSFSTVVLARELATSREYAIKILEKRHIIKENKVPYVTRERDVMS 135 Query:123 YL  124  L Sbjct: 136 EL  137 Score = 230 (106.0 bits), Expect= 1.4e−104, Sun F (S) = 1.4e−104 Identities = 39/90 (43%), Positives= 63/90 (70%) Query: 131HFFVTQLYTHFHDQARIYFVIGLVENGDLGESLCHFGSFDMLTSKFFASEILTGLQFLHD 190HPF  +LY  F D  ++YF +   +NG+L + +   GSFD   ++F+ +EI++ L++LH Sbjct: 139HPFFVKLYFTFQDDEKLYFGLSYAKNGELLKYIRKIGSFDETCTRFYTAEIVSALEYLHG 198 Query:191 NKIVHRDMKPDNVLIQKDGHILITDFGSAQ  220   I+HRD+KP+N+L+ +D HI ITDFG+A+Sbjct: 199 KGTTHRDLKPENILLNEDMHIQITDFGTAK  228 Score = 238 (109.7 bits),Expect = 1.4e−104, Sum F (S) = 1.4e−104 Identities = 43/98 (43%),Positives = 67/98 (68%) Query: 259EENTARRTTFVGTALYVSPEMLADGDVGPQTDIWGLGCILFQCLAGQPPFRAVNQYHLLK 318E   AR  +FVGTA YVSPE+L +      +D+W LGCI++Q +AG PPFRA N+Y + + Sbjct: 233ESKQARANSFVGTAQYVSPELLTEKSACKSSDLWALGCIIYQLVAGLPPFRAGNEYLIFQ 292 Query:319 RIQELDFSFPEGFPEEASEIIAKILVRDPSTRITSQEL  356+I +L++ FPE F  +A +++ K+LV D + R+  +E+ Sbjct: 293KTTKLEYDFPEKFFPKARDLVEKLLVLDATKRLGCEEM  330 Score = 85 (39.2 bits),Expect = 1.4e−104, Sun F (S) = 1.4e−104 Identities = 17/35 (48%),Positives = 21/35 (60%) Query: 356 LMAHKFFENVDWVNIANIKPPVLHAYIPATFGEPE390 L AH FFE+V W N+    PP L AY+PA   + E Sbjct: 336LKAHPFFESVTWENLHQQTPPKLTAYLPAMSEDDE 370 Score = 324 (149.3 bits), Expect= 1.4e−104, Sum P (5) = 1.4e−104 Identities = 59/104 (56%), Positives= 75/104 (72%) Query: 458LEEQRVKNPFHIFTNNSLILKQGYLEKKRGLFARRRMFLLTEGPELLYIDVPNLVLKGEV 517LE+Q   NP+H F  N+LILK G ++K++GLFARRR  LLTEGPHL Y+D  N VLKGE+ Sbjct: 439LEKQAGGNPWHQFVENNLILKMGPVDKRKGLFARRRQLLLTEGPHLYYVDPVNKVLKGEI 498 Query:518 PWTPCMQVELKNSGTFFIETPNRVYYLFDLEKKADEWCKAINDV  561PW+  ++ E KN  TFF+HTPNR YYL D    A +WC+ I +V Sbjct: 499PWSQELRPEAKNFKTFFVHTPNRTYYLMDPSGNAHKWCRKIQEV  542

Mapping of the mg142 mutation to this open reading frame establishes thefunction of this protein. It is much more closely related to PDK than toany other known kinase. PDK is a mammalian kinase that phosphorylates anessential serine residue on AKT, contributing to its activation. Theregion of akt-1 phosphorylated by PDK-1 is shown below (SEQ IDNOS:203–207 and 305).

human AKT 276 KLENLMLDKDGHIKITDFGLCKEGIKDGATMKTFCGTPEYLAREV 320KLENL+LDKDGHIKI DFGLCKE I G     TFCGTPEYLAFEV Ce akt-1 33509KLENLLLDKDGHIKIADFCLCKEEISFCDKTSTFCGTPEYLAPEV 33643 Ceakt2 326LCKEEIKYGDKTSTFCGTPEYLAFEVIEDIDYDRSVDWWGVGVVMYEMMCGRLPFSAKENGKLCKE I G     TFCGTPEYLAPEV+ED DYR+VDWWG+GVVMYEMMCGRLPF  +++ + moAKT: 298LCKEGISDGATMKTFCGTPEYLAPEVLEDNDYCRAVDWWGLGVVMYEMMCGRLPFYNQDHER

The phosphorylated serine is conserved in akt-1 and akt-2. Thus, PDK isan excellent candidate gene for the mg142 mutation. The genetic regionbearing pdk-1 was amplified from the mg142 strain, and an amino acidsubstitution in a conserved region of the PDK kinase domain wasdetected. While a gain of function mutation in pdk would be consistentwith the biochemical work that shows that PDK acts upstream of AKT toactivate it, this genetic work suggests that, if PDK can be activated(for example, by the mg142 mutation), no PIP3 signaling from the AGE-1PI3K is necessary, since mg142 suppresses an age-1 null allele. Toestablish that this substitution causes the suppression of age-1 induceddauer arrest, a strategy analogous to that used to analyze theakt-1(mg144gf) mutation may be utilized.

Because we have implicated PDK in the C. elegans insulin signalingpathway, human PDK1 becomes a candidate gene for variation in diabetes.Mutations in human PDK1 may underlie the genetic variation that causesdiabetes in some families. Similarly, drugs that activate PDK, like themg142 mutation that activates C. elegans pdk-1, may bypass the need forupstream signaling in some diabetics with such upstream defects. Theregion of human PDK1 that is homologous to the C. elegans pdk-1 atalanine 303 provides a good candidate for screening for drugs that bindand activate signaling. Similarly, the region of human AKT between thekinase domain and the PH domain, where the C. elegans akt-1 gain offunction mutation maps is a good candidate for the design of drugs thatactivate AKT. Exemplary screens identify daf-2 receptor mutations thatare capable of reproductive growth or age-1; daf-18 mutants that arrestat dauer stage. Such activated AKT in C. elegans bypasses the need forupstream signaling from the AGE-1 PI3K and may similarly treat diabeticswith defects in insulin signaling between insulin and AKT.

In addition, another mutation, pdk-1(lof), has been identified as a Glyto Arg substitution at position 295. This mutation causes dauer arrestin an otherwise wild-type background. This and the mg142 mutation arelocated near the psuedosubstrate binding region of PDK-1, based on thecrystal structure of PKA. It is likely that the G to R mutationdisallows recognition of the substrate AKT-1 and AKT-2, whereas the A toV gain of function mutation may disallow recognition of apsuedosubstrate site on PDK but allow recognition of the substrate,AKT-1 and AKT-2.

Our gain of function mutations in PDK-1 and AKT-1 point to negativeregulatory domains of these proteins. For example, the region flankingthe akt-1(mg144) mutation in the nonconserved domain of akt-1 maymediate blocking of the kinase activity, so that when this region ismutant, the kinase is more active. Similarly the region flanking thepdk-1(mg142) mutations in the conserved kinase domain may promiscouslyactivate pdk-1. This region is conserved in human pdk-1 and may exposethe kinase domain to the substrates, AKT-1 and AKT-2, constitutively.Chemicals that target the homologous or analogous domains in the humanhomologues of AKT-1, AKT-2, and PDK-1 may activate these kinases,bypassing the need for upstream insulin input and ameliorating theglucose intolerance.

Function of the Insulin-Like Pathway in Neurons

In addition to the above results, we have also found that the dauerarrest and aging effects of defects in age-1 signaling can becomplemented by expression of this gene in the nervous system only. Weused the nervous system-specific promoter unc-14 to drive expression ofan age-1 cDNA. The age-1 fusion genes were placed in an age-1 nullmutant, mg44, which arrests at the dauer stage 100% of the time andshifts to fat storage metabolism if no maternal or zygotic age-1 issupplied. Expression of age-1 in just the nervous system in this mutantcompletely complemented the dauer arrest and long lifespan phenotypesand partially complemented the metabolic fat storage defect. Theexpression of age-1 from a ubiquitous promoter, dpy-30, rescued all ofthe defects of an age-1 mg44 null mutant. In parallel experiments, twodifferent nervous system promoters, unc-14 and unc-119, were used todrive expression of daf-2 cDNA in daf-2 mutant animals. However,neuronal expression of DAF-2 did not rescue the aging or metabolicphenotypes of the daf-2 mutants. Given the multiple insulin-like ligandsfor DAF-2, these results may indicate that there is differentialsplicing of this receptor so that the cDNA introduced in theseexperiments supplied only one functional isoform. On the other hand,age-1 rescues all phenotypes when expressed ubiquitously, arguingagainst a differential splicing mechanism.

These data indicate that the insulin signaling pathway can regulatedauer arrest from the nervous system and may also regulate aging fromthe nervous system. The data also show that this pathway may function aswell in target tissues to regulate metabolism. It is likely that thesame situation may be true of mammalian insulin like signaling: theeffects of insulin on aging may be in the nervous system whereas theirwell known effects on muscle and adipocyte metabolism may be akin to theDAF-2/AGE-1 regulation of metabolism from non-neuronal foci of action.

Diapause and Longevity

Weak daf-2 and age-1 mutants that do not arrest at the dauer stagenevertheless live much longer than wild-type (Larsen et al., Genetics139: 1567–1583, 1995; Kenyon et al., Nature 366: 461–464, 1993; Dormanet al., Genetics 141: 1399–1406, 1995). This connection betweenlongevity and diapause control may not be unique to C. elegans. Diapausearrest is an essential feature of many vertebrate and invertebrate lifecycles, especially in regions with seasonal temperature and humidityextremes (Tauber et al., Seasonal Adaptation of Insects, OxfordUniversity Press, New York, N.Y., 1986). Animals in diapause arrest slowtheir metabolism and their rates of aging, and can survive for periodsfor much longer than their reproductive lifespan (Tauber et al., supra,1986).

Because insulin-like DAF-2/AGE-1 signaling mediates C. elegans diapauselongevity control, the mammalian insulin signaling pathway may alsocontrol longevity homologously. In fact, the increase in longevityassociated with decreased DAF-2 signaling is analogous to mammalianlongevity increases associated with caloric restriction (Finch,Longevity, Senescence and the Genome, The University of Chicago Press,Chicago, 1990). It is possible that caloric restriction causes a declinein insulin signaling to induce a partial diapause state, like thatinduced in weak daf-2 and age-1 mutants. The induction of diapause-likestates may affect post-reproductive longevity (Finch, supra), as in C.elegans. Alternatively, it is the changes in the mode and tempo ofmetabolism itself rather than diapause per se that causes increasedlongevity. Another long-lived C. elegans mutant, clk-1, may alsoregulate lifespan via such metabolic effects (Ewbank et al., Science275: 980–983, 1997). This association of metabolic rate with longevityis also consistent with the correlation of free radical generation toaging (Finch, supra).

Daf-18 Suppresses the Metabolic and Dauer Phenotypes of Age-1 and Daf-2

In addition to the genes described above, we have also discovered thatdaf-18 functions in the insulin signaling cascade as follows. age-1 nullmutant progeny of heterozygote mothers are maternally rescued for arrestat the dauer diapause stage (Gottlieb and Ruvkun (1994) Genetics137:107–120), but not for accumulation of fat (FIG. 38D) or increasedlongevity (Gottlieb and Ruvkun (1994) Genetics 137:107–120). The progenyof these fat and long lived age-1 homozygous animals, which receive nomaternal or zygotic AGE-1 PI3K activity, arrest development as dauerlarvae (Morris et al. (1996) Nature 382:536–539) (Tables VII and VIII).

TABLE VII Suppression of daf-18 by inhibition of akt-1 and akt-2 geneactivity Phenotype of Progeny at 25° C. (%) dsRNA L4 and Strain injectedAdult Dauer Other N Wild type (Bristol uninjected 99.8 0 0.2 1040 N2)Wild type (Bristol akt-1 & akt-2 13.7 85.9 0.3 2199 N2) daf-18(e1375)uninjected 99.1 0 0.9 1213 daf-18(e1375) akt-1 & akt-2 23.2 76.6 0.21455 daf-16(mgDf50) uninjected 99.9 0 0.1 1266 daf-16(mgDf50) akt-1 &akt-2 97.5 0 2.5 1970 age-1(mg44) uninjected 0 99.5 0.4 228 age-1(mg44)akt-1 & akt-2 0 94.2 5.8 277 age-1(mg44); daf-18 uninjected 99.3 0.7 0274 (e1375) age-1(mg44); daf-18 akt-1 & akt-2 14.4 85.0 0.7 592 (e1375)daf-16(mgDf50); uninjected 100 0 0 465 age-1 (mg44) daf-16(mgDf50);akt-1 & akt-2 96.2 0 3.8 1098 age-1 (mg44) daf-2(e1370) uninjected 099.1 0.9 109 daf-2(e1370) akt-1 & akt-2 0 100 0 176 daf-2(e1370);uninjected 2.2 97.8 0 225 daf 18(e1375) daf-2(e1370); akt-1 & akt-2 099.9 0.1 682 daf 18(e1375) daf-16(mgDf50); uninjected 100 0 0 487daf-2(e1370) daf-16(mgDf50); akt-1 & akt-2 99.1 0 0.9 780 daf-2(e1370)‘Other’ includes animals that could not be classified as dauer ornon-dauer because the animal died as an embryo or young larva. N, totalnumber of animals scored.

TABLE VIII Suppression of age-1 and daf-2 by inhibition of daf-18 geneactivity Phenotype of Progeny at 23° C. (%) dsRNA L4 and Strain injectedAdult Dauer Other N Wild type (Bristol N2) uninjected 100 0 0 763 Wildtype (Bristol N2) daf-18 99.4 0 0.6 1305 age-1(m333) uninjected 0 100 0434 age-1(m333) daf-18 94.2 5.6 0.3 771 age-1(mg109) uninjected 0 99.40.6 172 age-1(mg109) daf-18 94.7 0.3 5.0 341 age-1(mg44) uninjected 097.9 2.1 389 age-1(mg44) daf-18 90.7 7.1 2.1 701 age-1(mg44); daf-18uninjected 99.8 0 0.2 569 (e1375) daf-2(e1370) uninjected 0 100 0 606daf-2(e1370) daf-18 57.7 39.8 2.5 1266 daf-2(e1370); daf-18 uninjected6.3 93.7 0 317 (e1375) ‘Other’ includes animals that could not beclassified as dauer or non-dauer because the animal died as an embryo oryoung larva. N, total number of animals scored.Dauer larvae accumulate large amounts of fat (FIG. 38E) and live muchlonger than reproductively growing animals (Klass and Hirsh (1976)Nature 260:523–525). The dauer arrest (Gottlieb and Ruvkun (1994)Genetics 137:107–120; Larsen et al. (1995) Genetics 139:1567–1583;Tables VII and VIII), fat accumulation (FIG. 38F) and longevityphenotypes (Larsen et al. (1995) Genetics 139:1567–1583) of age-1 nullmutations are suppressed by daf-18(e1375). daf-18(e1375) gene activitydoes not appear to interfere with normal age-1 signaling and growthbecause daf-18(e1375) mutant animals in a wild type age-1 backgroundaccumulate wild type amounts of fat (FIG. 38B).

Although daf-18(e1375) behaves as a semi-dominant suppressor of age-1,it phenocopies inactivation of daf-18(+) gene activity by RNAinterference (RNAi) (see below). This suggests that daf-18(e1375) is aloss-of-function allele that is either haploinsufficient or dominantlyantimorphic. The bypass of the normal requirement for AGE-1 PI3Ksignaling by daf-18(e1375) suggests that either lack of AGE-1 activitycauses increased daf-18 activity or that decreased daf-18 activityincreases PIP3 signals in an AGE-1-independent manner.

Although daf-18(e1375) readily suppresses age-1 mutations for themetabolic, dauer, and longevity phenotypes, daf-18(e1375) is a lesseffective suppressor of daf-2 insulin receptor-like mutations (Dorman etal. (1995) Genetics 141:1399–1406; Larsen et al. (1995) Genetics139:1567–1583 and Tables VII and V1II). This is similar to thegain-of-function akt-1(mg144) which can suppress age-1 null mutants, butnot daf-2 mutants (Paradis and Ruvkun (1998) Genes Dev. 12:2488–2498).Like the increase in akt-1 gene activity induced by akt-1(mg144), thedecrease in daf-18 gene activity caused by daf-18(e1375) can bypass thenormal requirement for AGE-1 PI3K signaling, but not for DAF-2 insulinreceptor-like signaling (Tables VII and VIII). As in the case ofbiochemically studied receptor tyrosine kinases, the DAF-2 receptor mayhave multiple parallel outputs, with AGE-1, AKT-1/AKT-2, and DAF-18acting in one of these pathways. Signals from DAF-2 converge at theDAF-16 Fork head transcription factor, because null mutations in daf-16suppress all known phenotypes of daf-2 and age-1 null mutations (Ogg etal. (1997) Nature 389:994–999; Tables VII and VIII).

Daf-18 Functions Upstream of Akt-1 and Akt-2

In contrast to the action of DAF-2 and AGE-1, AKT-1 and AKT-2 actdownstream of DAF-18. akt-1 and akt-2 function redundantly in theregulation of dauer arrest. Inhibition of both gene activities in wildtype animals by RNAi causes constitutive dauer arrest, whereasinhibition of either akt-1 or akt-2 alone does not (Paradis and Ruvkun(1998) Genes Dev. 12:2488–2498). Inhibition of akt-1 and akt-2 by RNAicauses dauer arrest in either daf-18 or wild type animals (77% and 86%,respectively, Table VII). In contrast, 0% of daf-16(mgDf50) animalsarrest as dauers when akt-1 and akt-2 are inhibited (Paradis and Ruvkun(1998) Genes Dev. 12:2488–2498 and Table VII). Thus mutations in daf-18do not bypass the normal requirement for akt-1 and akt-2 activity. Thesedata suggest that daf-18 functions upstream or parallel to akt-1 andakt-2.

The suppression of age-1 null mutations by daf-18(e1375) is alsodependent upon akt-1 and akt-2. No progeny of age-1(mg44) null mutanthomozygous animals develop to become fertile adults (99% dauer larvae,Table VII). In contrast, few age-1(mg44); daf-18(e1375) animals arrestas dauers (0.7% dauer larvae, Table VII), instead of developing intoreproductive adults. However, when akt-1 and akt-2 are inhibited by RNAiin age-1(mg44); daf-18(e1375), most progeny arrest at the dauer stage(85% dauers, Table VII). The weaker suppression of daf-2 by daf-18 isalso dependent upon akt-1 and akt-2 (Table VII). These data suggest thatthe ability of daf-18 to suppress defects in insulin-like signaling isdependent upon akt-1 and/or akt-2, showing that daf-18 acts downstreamof AGE-1 PI3K, but upstream of AKT-1 and AKT-2 in this signalingcascade.

Daf-18 Encodes a Homologue of Mammalian PTEN (MMAC1/TEP1)

Daf-18 maps to a genetic region (Larsen et al. (1995) Genetics139:1567–1583) which bears the probable C. elegans homologue (T07A9.6)of the tumor suppressor gene PTEN (Li and Sun (1997) Cancer Res.57:2124–2129; Li et al. (1997) Science 275:1943–1947; and Steck et al.(1997) Nat. Genet. 15:356–362). Consistent with the role of PTEN as adaf-18 homologue is the fact that PTEN has lipid phosphatase activitythat dephosphorylates position 3 on the inositol ring of PIP₃ in vitroand decreases the levels of the lipid products of PI3K in response toinsulin signaling in human 293 cells (Maehama and Dixon (1998) J. Biol.Chem. 273:13375–13378). Accordingly, a decrease in PTEN activity wouldbe predicted to enhance PI3K signaling, consistent with daf-18 activity.Genetic mapping, the detection of the daf-18(e1375) mutation in thisPTEN homologue, and the similar phenotype to daf-18(e1375) caused byRNAi of this PTEN homologue all demonstrate that daf-18 corresponds tothis gene.

The sequence of a full length daf-18 cDNA predicts a protein of 962amino acids (FIGS. 40A and 40B). Homology between DAF-18 and human PTEN(U93051; Li et al. (1997) Science 275:1943–1947) is highest within thephosphatase domain (38% identical, 94/250 aa) which is located at theamino-terminal end of both proteins (FIGS. 39A and 39B). Amino acidssurrounding the probable active site Cys-(X)₅-Arg sequence are 90%identical (18/20 aa) between DAF-18 and PTEN (FIG. 39B). This suggeststhat the substrate specificity of DAF-18 and PTEN may be similar.

Using the canonical daf-18 PTEN cDNA sequences and genomic sequence fromthe C. elegans Genome Sequencing Consortium, the coding region andintron/exon boundaries of daf-18 were sequenced in daf-18(e1375) andcompared to the sequence of wild type. A 30 base pair insertion mutationwas detected in daf-18(e1375) (FIG. 39A). This insertion mutation occurswithin exon 4 and is predicted to insert 6 amino acids to the codingsequence before introducing a stop codon. The insertion is composed of athirteen base pair repeat and two smaller repeat segments. The mutationis predicted to leave the phosphatase domain intact, but to truncate thecarboxy-terminal half of the protein. Since the mutation maps to anunconserved domain and because inhibition of daf-18 by RNAi is moresevere than daf-18(e1375) (see below), it is unlikely that daf-18(e1375)is a null mutant.

Although many of the oncogenic human PTEN mutations map to thephosphatase domain, several have been identified in the carboxy-terminalhalf of the protein (see the Human Gene Mutation Database and referencestherein; Krawczak and Cooper (1997) Trends Genet. 13:121–2). Thesecarboxy-terminal mutations are analogous to daf-18(e1375). Since someoncogenic mutations in PTEN and the daf-18(e1375) allele are localizedto the carboxyl-terminal end, these regions, though unconserved betweenC. elegans and mammals, may be critical for phosphatase localization orfunction.

Daf-18(e1375) is the only identified daf-18 allele, despite theextensive genetic screens that have been done for genes in the dafpathway. Additional daf-18 alleles have not been isolated in screens forsuppressors of daf-2 (in contrast to the scores of daf-16 alleles),which may be due to the weak suppression of daf-2 by daf-18(e1375)(Tables VII and VIII). Because of the strong suppression of age-1 nullmutants by daf-18(e1375), more alleles would be expected from screensfor age-1 suppressor mutations.

The daf-18(e1375) allele causes other phenotypes besides suppression ofthe age-1 null mutant. 8% of daf-18(e1375) animals (n=831) die as adultswith a burst vulva compared to 0% of wild type (Bristol N2) adults(n=920) grown at 23° C. This suggests that daf-18 may function in othersignal transduction pathways. Consistent with this, a daf-18promoter::green fluorescent protein fusion is expressed in many tissuesthroughout the animal.

Inactivation of Daf-18 by RNAi Suppresses Age-1 and Daf-2

Inactivation of the C. elegans PTEN homologue T07A9.6 by RNAi confirmsthe assignment of daf-18 to the gene and the assignment of daf-18 to afunction downstream of age-1 PI3K and upstream of akt-1 and akt-2. Theinactivation of daf-18 by RNAi potently suppresses null mutations inage-1 and more weakly suppresses a daf-2 insulin receptor-like mutant.Whereas the homozygous progeny of three different age-1 mutant alleles,including two null alleles, arrest at the dauer stage virtually 100% ofthe time (Dorman et al. (1995) Genetics 141:1399–1406; Larsen et al.(1995) Genetics 139:1567–1583 and Table VIII), inhibition of daf-18 byRNAi suppresses the dauer constitutive phenotype of age-1(m333),age-1(mg109) and age-1(mg44) (only 6%, 1% and 8% dauers, respectively)(Table VIII). This is comparable to the suppression of age-1(mg44) bydaf-18(e1375) (0% dauers, Table VIII).

Inhibition of daf-18 PTEN by RNAi partially suppresses aloss-of-function allele of the daf-2 insulin receptor-like gene. Thissuppression is most easily observed under conditions where daf-2 geneactivity is decreased, but probably not missing. daf-2(e1370) is atemperature sensitive allele with a mutation in the kinase domain(Kimura et al. (1997) Science 277:942–946). At a low temperature (15°C.), daf-2(e1370) animals do not form dauers, but more restrictivetemperatures (25° C. or 23° C.) cause 100% arrest at the dauer stage(Tables VII and VIII). The arrest of daf-2(e1370) at 23° C. is weaklysuppressed by daf-18(e1375) (94% dauers), but inhibition of daf-18(+) byRNAi suppresses daf-2(e1370) much more potently (40% dauers) (TableVIII). At 25° C., daf-18(e1375) is a weaker daf-2 suppressor, suggestingthat DAF-2 insulin receptor-like outputs, parallel to the AGE-1 PI3K,DAF-18 PTEN, and AKT-1/2 pathways, are more essential at this highertemperature. In contrast, the daf-16(mgDf50) null mutation completelysuppresses daf-2(e1370) at all temperatures (0% dauers, Tables VII andVIII). This suggests that divergent signals from DAF-2(AGE-1/DAF-18/AKT-1/2 and another putative pathway) converge uponDAF-16.

These results suggest that daf-18(e1375) is a partial loss-of-functionmutation and that inhibition of daf-18 by RNAi causes a larger decreasein daf-18 gene activity. Similar to daf-18(e1375), the inhibition ofdaf-18 gene activity in wild type causes some animals to burst at thevulva, but no other obvious phenotypes. The inhibition of daf-18 geneactivity by RNAi, however, does not necessarily reveal the phenotypeinduced by the complete loss of daf-18 gene activity.

Assignment of Daf-18 to the DAF-2 Signaling Pathway

Our assignment of the daf-18 molecular function to a homologue of thePTEN lipid phosphatase fits into our genetic analysis of its action inthe DAF-2 insulin receptor-like signaling pathway. The genetic pathwayanalysis shows that DAF-18 is likely to act between the AGE-1 PI3K andAKT-1/AKT-2. Because PTEN has been shown to dephosphorylate position 3of the inositol ring of PIP3, DAF-18 may modulate DAF-2 signals bydecreasing the PIP3 output of AGE-1 PI3K. DAF-18 may normally decreasethe level of PIP3 signals, perhaps insulating signals emanating from theDAF-2/AGE-1 signaling complex from other PIP3 signals in the cell, orresolving insulin-like signaling episodes by restoring lipid levels topre-insulin status. Perhaps the long carboxyl-terminal tail region ofDAF-18 PTEN mediates its localization to insulin signaling complexes,insulating them from other signaling complexes, or vice versa. Loss ofDAF-18 would be expected to enhance PIP3 signaling to the Akt kinases byallowing the second messenger to promiscuously signal between receptorcomplexes.

It is not clear from the genetic analysis whether DAF-18/PTEN activityis regulated during insulin-like or other signaling. For example, theremay be phosphorylation input to activate or inactivate DAF-18 activity.One attractive possibility is that DAF-18 becomes activated by Akt orPDK1 as a component in the recovery from an episode of insulinsignaling. It may be significant that PTEN lipid phosphatase activity invitro is low (Maehama and Dixon (1998) J. Biol. Chem. 273:13375–13378),perhaps due to a missing modification by the insulin signaling cascade.

DAF-18 may also be regulated by a TGF-β signaling pathway. In C. elegansa TGF-β signaling pathway converges with the DAF-2 insulin receptor-likesignaling pathway (Ogg et al. (1997) Nature 389:994–999) and PTENexpression has been reported to be downregulated by TGF-β signaling incell culture (Li and Sun (1997) Cancer Res. 57:2124–2129). The C.elegans DAF-7 TGF-β and insulin-like signaling pathways are alsosynergistic, whereby declines in the TGF-β signals enhance the mutantphenotypes caused by declines in insulin-like signals (Ogg et al. (1997)Nature 389:994–999). If DAF-18 PTEN expression is similarly responsiveto DAF-7 TGF-β inputs, its activity may mediate cross talk between thesepathways in metabolic control.

The molecular assignment of DAF-18 to the PTEN lipid phosphataserationalizes daf-18 genetic activities in C. elegans metabolic controland longevity. Reduction of daf-18 gene activity causes a decrease infat storage in an age-1 mutant, perhaps because the ensuing activationof AKT-1 and AKT-2 mimics that induced by insulin-like signaling,causing a shift from fat storage metabolism to reproductive, perhapssugar-based, metabolism. The daf-18(e1375) mutation also stronglysuppresses the longevity increase caused by the weak age-1(hx546) PI3Kmutation or the weak daf-2(e1370) insulin receptor-like mutation at asemi-permissive temperature (Dorman et al., (1995) Genetics141:1399–1406; Larsen et al. (1995) Genetics 139:1567–1583), whereasdaf-18(e1375) only weakly suppresses the longevity increase caused bynull age-1 mutations or daf-2(e1370) at the non-permissive temperature(Dorman et al., (1995) Genetics 141:1399–1406; Larsen et al. (1995)Genetics 139:1567–1583). These data show that even though the increasein PIP₃ levels caused by a decrease in daf-18 gene activity can bypassthe need for AGE-1 signaling in dauer arrest, the resulting level ofPIP₃ is not sufficient to induce normal aging. These results arecongruent with aging and dauer arrest phenotypes of an age-1 allelicseries: the highest levels of age-1 (i.e., PIP₃) are necessary fornormal longevity, whereas animals with decreased but non-zero levels ofPIP₃ age more slowly, but do not arrest at the dauer stage. And onlywhen both zygotic and maternal AGE-1 is missing do PIP₃ levels declineto the point that animals arrest at the dauer stage (Gottlieb and Ruvkun(1994) Genetics 137:107–120; and Riddle (1988) The Dauer Larva. In TheNematode Caenorhabditis elegans, W. B. Wood, ed. (Cold Spring Harbor,N.Y.: Cold Spring Harbor Laboratory), pp. 393–412). We have not yetdetermined whether the regulation of metabolism is the cause of thelongevity phenotype (or vice versa) or represents a co-regulated outputof the DAF-2 insulin receptor-like pathway.

This genetic behavior is similar to that of activated AKT-1, which cansuppress the dauer arrest caused by complete lack of AGE-1 PI3Ksignaling, but not the longevity increase (Paradis and Ruvkun (1998)Genes Dev. 12:2488–2498). The suppression of the age-1 null mutantmetabolic phenotypes by daf-18, but not by the akt-1 gain-of-functionmutation, suggests that an increase in PI(3,4)P₂ and PIP₃ levels is acloser mimic to wild type than activated AKT-1, perhaps because bothAKT-1 and AKT-2 are activated by increased lipid signaling in a daf-18mutant. It may also be significant that declines in daf-18 activity andthe presumed concommitant increase in PI(3,4)P₂ and PIP₃ levels in wildtype has a negligible effect on longevity (Dorman et al., (1995)Genetics 141:1399–1406; Larsen et al. (1995) Genetics 139:1567–1583).Presumably, once PIP₃ levels are above a threshold, increasing theirlevels does not influence lifespan.

Our molecular model suggests that DAF-2, AGE-1, DAF-18, AKT-1, AKT-2,and DAF-16 act in the same cells. It has not addressed whether thesegenes in fact act in the same cells nor have we discerned whether thispathway acts in key endocrine signaling cells or in target tissues.daf-18, akt-1, and daf-16 are all expressed in neurons and throughoutmuch of the animal (Ogg et al. (1997) Nature 389:994–999; Paradis andRuvkun (1998) Genes Dev. 12:2488–2498), consistent with their functioneither in signaling cells or target tissues.

Inhibition of daf-18 can suppress age-1 mutations (m333 and mg44) thatare predicted to truncate AGE-1 before the kinase domain and thereforegenerate no PIP₃ at all (Morris et al. (1996) Nature 382:536–539); TableVIII). The ability of daf-18 inhibition to suppress age-1 nullmutations, and our demonstration that daf-18 suppression depends on theAkt kinases, suggests that there must be another source of PI(3,4)P₂ orPIP₃. This alternative source of lipids is not normally redundant withthose generated by DAF-2/AGE-1 signaling because age-1 mutations havemetabolism, reproductive growth, and lifespan phenotypes. In the absenceof daf-18, lipids may accumulate to levels sufficient to activate theAkt kinases.

In addition to AGE-1, there are two other PI3K genes in the C. elegansgenome. AGE-1 is the only member of the “Type I” class that includes the110–130 kilodalton catalytic/50–85 or 101 kilodalton adaptorheterodimers (Vanhaesebroeck et al. (1997) TIBS 22:267–272). Members ofthis class of PI3Ks are activated by growth factors and heterotrimericGTP-binding protein-coupled receptors and phosphorylatephosphatidylinositol, PI(4)P, and PI(4,5)P₂ to generate PI(3)P,PIP(3,4)P₂ and PIP₃ in vitro. PIP₃ may be dephosphorylated at the5-position to yield the actual PI(3,4)P₂ signal (Damen et al. (1996)Proc. Natl. Acad. Sci. U.S.A. 93:1689–93; Ono et al. (1996) Nature383:263–6). The “type II” class is represented in C. elegans by F39B1.1.Members of this class are defined by amino terminal extensions and a C2domain at their carboxy termini (Newton (1995) Curr. Biol. 5:973–6;Vanhaesebroeck et al. (1997) TIBS 22:267–272). C2 domains wereoriginally described as Ca²⁺-dependent phospholipid binding motifs, butthey have been found to bind lipid in a Ca²⁺-independent manner and mayalso mediate protein-protein interactions. Type II PI3Ks preferentiallyphosphorylate phosphatidylinositol and PI(4)P, over PI(4,5)P₂, togenerate PI(3)P and PI(3,4)P₂. “Type III” PI3Ks are related to yeastprotein VPS34 (Vanhaesebroeck et al. (1997) TIBS 22:267–272). Theseproteins have regulatory subunits and phosphorylatephosphatidylinositol, exclusively. Rather than being activated bycellular agonists, type III PI3Ks are thought to participate in vesiclesorting (De Camilli et al. (1996) Science 271:1533–9). The C. elegansgene, B0025.1, is most closely related to this family.

Since AGE-1 is the only known C. elegans type I PI3K, the type II PI3K,F39B1.1, may be the alternative source of 3-phosphorylatedphosphoinositides which can activate Akt. DAF-18 may normally insulateDAF-2/AGE-1 signaling from other PI(3,4)P₂ or PIP₃ second messengersignals in the cell. But when DAF-18 activity is inhibited, cross talkfrom this other PI3K may promiscuously activate the Akt kinases whichare normally dependent on AGE-1 PI3K generated PIP3.

Our placement of DAF-18/PTEN downstream from AGE-1 PI3K and upstreamfrom AKT-1 and AKT-2 suggests that mammalian PTEN may also regulate Aktactivity by modulating PI3K signals. In fact, recent experiments withPTEN knockout mutant mice have shown that PTEN acts upstream of Akt inmammalian growth factor signaling pathways (Stambolic et al. (1998) Cell95:29–39). More specifically, the action of DAF-18 PTEN in the C.elegans insulin signaling metabolic and longevity control pathwaysuggests that mammalian PTEN may modulate insulin control of metabolismand lifespan. Reduction in PTEN activity would be expected to potentiateinsulin and/or insulin-like growth factor signaling, but an increase ofPTEN activity would be expected to cause insulin resistance downstreamof the insulin receptor, the type observed in late onset diabetes. ThusPTEN on chromosome 10 is a candiate gene for human autosomal dominanttype II diabetes as well as for human longevity control.

Methods

The experiments described above were carried out using the followingmaterials and methods.

Strains

Alleles used were as follows: LGI daf-16(mgDf50); LG II sqt-1(sc13)age-1(mg44)/mnC1, unc-4(e120) age-1(m333)/mnC1, unc-4(e120)age-1(mg109)/mnC1; LGIII daf-2(e1370).

Sudan Black Staining

Larvae and young adults maintained in well fed conditions were washed inM9 buffer (Brenner (1974) Genetics 77:71–94) for 30 minutes, fixed in M9with 1% paraformaldehyde, and subjected to three freeze thaws. Animalswere then washed and dehydrated through washes with 25%, 50% and 70%ethanol. Staining was performed overnight in a 50% saturated solution ofSudan Black B in 70% EtOH. Stained animals were visualized with a ZeissAxioplan microscope.

RNA Interference (RNAi) and Dauer Arrest Assays

akt-1 and akt-2 RNAi was performed as described (Paradis and Ruvkun(1998) Genes Dev. 12:2488–2498). daf-18 RNAi was performed in a similarmanner. The full length daf-18 cDNA was amplified by PCR from yk400b8(Y. Kohara) using primers CM024 and CM025 (Paradis and Ruvkun (1998)Genes Dev. 12:2488–2498). RNA was transcribed using MEGAscript T3 and T7kit (Ambion) and then single stranded RNA was combined prior toinjection. L4 hermaphrodites or young adults were injected into the gutwith approximately 5 μg/μl double stranded RNA and then were allowed torecover overnight at the experimental temperature. To assay dauerarrest, single injected animals or uninjected L4 hermaphrodites or youngadults were moved to new plates and again on the next two subsequentdays. All progeny laid after the recovery period were scored two daysafter being laid as dead eggs, dauer larvae, L4 larvae, adults oranimals with aberrant development. “Dauers” included dauers and partialdauers as defined (Paradis and Ruvkun (1998) Genes Dev. 12:2488–2498).For the experiments with age-1 mutants, age-1 homozygous mutant progenyof age-1 heterozygous mothers were injected.

Sequencing

Genomic DNAs from daf-18(e1375) and wild type (Bristol N2) were PCRamplified and directly sequenced. A putative full length clone, yk400b8(gift from Y. Kohara), was fully sequenced. The sequence of this cloneand additional clones partially sequenced by Y. Kohara (yk423e3,yk400b8, yk419d6, yk282b4, yk226d6, yk219b10, yk200a11, yk181h9, yk49a4,and yk43e5) have a different exon/intron structure than was predictedfor T07A9.6 by Genefinder.

Drugs that Regulate DAF-18 PTEN Lipid Phosphatase in the Treatment ofDiabetes, Obesity, and Aming

Since DAF-18/PTEN is a lipid phosphatase, chemical modulation of itsactivity may be readily identified using any standard in vitro lipidphosphatase assay (see, for example, Maehama and Dixon, J. Biol. Chem.273:13375, 1998). Chemicals identified by this initial screen may thenbe tested in a C. elegans assay as described herein. These tests arebest done using the human homologue of DAF-18, the oncogene PTEN, bothin vitro and transformed into a C. elegans strain lacking daf-18 geneactivity (also as described herein). In particular, chemicals thatactivate human PTEN in vitro may be tested on C. elegans daf-18 mutantsexpressing human PTEN from the daf-18 promoter, assaying for dauerarrest, metabolic switch from fat storage, and/or increased longevity,either in an otherwise wild type background or in an age-1 or daf-2mutant background. If desired, chemicals that perturb longevity ormetabolism of such humanized C. elegans could also be tested on mice.

These chemicals would be expected to affect glucose and fat levels andtreat type II diabetes and obesity. In particular, chemicals thatactivate DAF-18 would be expected in increase longevity. In addition,even though such chemicals could affect the cell cycle, since PTEN is arecessive oncogene, skin creams that activate PTEN would be expected tohave youth enhancing activities. Conversely, chemicals that inhibitDAF-18 activity would be expected to treat type II diabetes and obesity,consistent with the fact that decreases in DAF-18 gene activitycompletely bypass the need for age-1 P13 kinase signaling and partiallybypass the need for daf-2 insulin receptor-like signaling. Thus, drugsthat inhibit human PTEN activity in vitro are preferably tested on C.elegans for the ability to bypass the need for age-1 PI3K signaling inan animal carrying human PTEN expressed from the daf-18 promoter. In oneparticular example, any drug that inhibited human PTEN activity wouldallow an age-1(0); daf-18(0) mutant strain carrying human PTEN expressedfrom the daf-18 promoter to grow reproductively, rather than arrestingin a manner characteristic of the parent strain. Thus, drugs shown toinhibit human PTEN in vitro could be tested on worms of the age-1(0);daf-18(0); daf-18 promoter/PTEN genotype for ability to allowreproductive growth. If desired, such drugs could then be tested fordiabetic therapeutic efficacy in mouse or rat models of obesity onsetdiabetes (as described herein). Drugs identified by this screen wouldtreat some type II diabetic patients as well as some obese patients withdefects in the PI3K outputs of the insulin receptor pathway.

Glucose Regulation by the C. elegans Insulin Like Signaling Pathway:Confirmation of its Applicability to Human Diabetes

We have constructed a full length protein fusion of GFP to a highlyexpressed glucose transporter orthologue in the worm genome: H17B01. TheH17B01.1 (GLUT) GFP fusion was amplified with primer CAW59(ccactatggccgagatttcc) (SEQ ID NO: 319) and CAW60(ccagtgaaaagttcttctcctttcttcctcttctcgaattcgga) (SEQ ID NO: 320). CAW 59is the promoter primer and corresponds to nucleotides 31101–31120 incosmid H17B01 and 39249–39268 in YAC Y51H7.contig253. Primer CAW60 isthe GFP-fusion primer. The first 23 nucleotides are GFP and the last 21are GLUT bottom strand (i.e., cttcctcttctcgaattcggc) (SEQ ID NO:321)corresponding to 48128–48108 in Y51H7.contig253 and 5015–5035 in C13F7(the cosmid that joins H17B01). The protein sequence is as follows (SEQID NO: 208):

MGVNDHDVSVPLQEVQSRTVEGKLTKCLAFSAFVITLASFQFGYHIGCVNAPGGLITEWIIGSHKDLFDKELSRENADLAWSVAVSVFAVGGMIGGLSSGWLADKVGRRGALFYNNLLALAAAALMGLAKSVGAYPMVILGRLIIGLNCGFSSALVPMFLTEISPNNLRGMIGSLHQLLVTIAILVSQIFGLPHLLGTGDRWPLIFAFTVVPAVLQLALLMLCPESPKYTMAVRGQRNEAESALKKLRDTEDVSTEIEAMQEEATAAGVQEKPKMGDMFKGALLWPMSIAIMMMLAQQLSGINVAMFYSTVIFRGAGLTGNEPFYATIGMGAVNVIMTLIAVWLVDHPKYGRRSLLLAGLTGMFVSTLLLVGALTIQNSGGDKWASYSAIGFVLLFVISFATGPGAIPWFFVSEIFDSSARGNANSLAVMVNWAANLLVGLTFLPINNLMQQYSFFIFSGFLAFFIFYTWKFVPETKGKSIIEQIQAEFEKRK

The predicted coiled-coil domain is from 237–258 (SEQ ID NO: 209):RNEAESALKKLRDTEDVSTEIE

-   This transporter contains a coiled coil domain in common with the    glut4 insulin responsive mammalian glucose transporter and the glut1    mammalian thrombin responsive glucose transporter of platelets. This    coiled coil domain may mediate the tethering of these subfamily of    glucose transporters adjacent to the plasma membrane so that these    transporters can be fused upon triggering signals, for example, from    insulin.

We have verified that the localization of the H17B01 glucose transporteris responsive to daf-2 insulin like signaling. In particular, thetransporter is suspended in vesicles in a daf-2 mutant but is placed inthe cell membrane in wild type animals with normal insulin likesignaling. The insulin responsive fusion of these transporters with thecell membrane is most easily observed in the nervous system of C.elegans. This discovery endorses the glucoregulatory role of DAF-2insulin like signaling in C. elegans, further confirming the orthologywith mammalian insulin regulation of glucose transport. It also pointsout a possible regulatory role for glucose transport in the nervoussystem. It is possible that the regulation of sugar metabolism byinsulin in the brain may be more important in humans than has previouslybeen appreciated. The study of human insulin responses have been focusedon peripheral tissues, but it is entirely possible that the centralresponses to insulin are key in the disease progression.

We have also shown that the glucose transporter genes of C. elegans aretranscriptionally responsive to insulin signaling. The promoter of thisgene is a good candidate for finding DAF-16 binding sites and DAF-3binding sites. In mammals, glucose transporters are transcriptionallyregulated by insulin signaling, suggesting that the connection betweenDAF-16 and the glucose transporter may be general to the DAF-16homologues, AFX, FKHR, and FKHRL1 and mammalian glucose transporterssuch as Glut4 whose transcription is regulated by insulin. Indeed wefind that the expression of the glucose transporter GFP fusion isdownregulated in starved wild type animals but is not so downregulatedin daf-16 mutant animals, suggesting that it is daf-16 activity thatrepresses the expression of this gene.

Synergistic Control of Metabolism and Diapause by Insulin and TGF-βSignaling Pathways

In addition to DAF-2 signaling, the DAF-7 TGF-β neuroendocrine signal isalso necessary for reproductive development of C. elegans (Ren et al.,Science 274: 1389–1391, 1996; Schackwitz et al., Neuron 17: 719–728,1996). The signals in these two pathways are not redundant: animalsmissing either daf-2 signaling or daf-7 signaling (FIG. 3) shift theirmetabolism and arrest at the dauer stage (Table IX). In addition thephenotypes caused by mutations in either pathway are stronglysynergistic, suggesting that the two pathways are integrated.Synchronised eggs were grown and counted as described above. daf-1(m40)and daf-2(e1370) form 100% dauer at 25° C. Numbers shown in Table IXindicate percentage dauer formation and number of animals counted (inparenthesis). Data presented is the sum of three independent trials.

TABLE IX Synergy of daf-1 and daf-2 % dauer formation ° C. 20° C. daf-1(m40)  0.0 (532) 1.9 (909) daf-2 (e1370)  0.0 (798) 3.8 (503) daf-1(m40); 19.4 (747) 100 (718) daf-2 (e1370)This data indicates that DAF-7 TGF-β signals and DAF-2 ligandinsulin-like signals are integrated. In support of this model, weakmutations in the daf-2 insulin signaling pathway and in the daf-7 TGF-βsignaling pathway are highly synergistic (Table IX). Genetic epistasisanalysis indicates that the DAF-7 and DAF-2 pathways are parallel ratherthan sequential (Vowels and Thomas, Genetics 130: 105–123, 1992;Gottlieb and Ruvkun, Genetics 137: 107–120, 1994). That is, daf-16mutations strongly suppress daf-2 mutations but not daf-7, daf-1, ordaf-4 mutations, whereas daf-3 mutations strongly suppress daf-7, daf-1,and daf-4 mutations, but not daf-2 mutations. Analogous synergismbetween activin and FGF tyrosine kinase pathways in Xenopus mesoderminduction has been noted (Green et al., Cell 71: 731–739, 1992).

A dauer-inducing pheromone regulates the production of DAF-7 by the ASIsensory neuron (Ren et al., Science 274: 1389–1391, 1996; Schackwitz etal., Neuron 17: 719–728, 1996). Because animals carrying daf-7 nonsenseor truncation mutations are responsive to pheromone (Golden and Riddle,Proc. Natl. Acad. Sci. U.S.A. 81: 819–823, 1984), we further suggestthat the production of the insulin-like ligand for DAF-2 is alsoregulated by pheromone. It is not yet clear whether these DAF-7 andDAF-2 signals converge in target tissues or in other regulatory (i.e.,hormonal) cells; however the expression of the DAF-7 receptor pathwaygenes in essentially all target tissues (infra) suggests thatintegration occurs there.

DAF-7 and Diabetes

Based on the data herein, we propose that in humans as in C. elegans,both a DAF-7-like neuroendocrine signal and insulin are necessary formetabolic control by insulin. According to this model, the failure oftarget tissues to respond to insulin signals in Type II diabeticpatients could be due to defects either in the insulin or TGF-β-likecontrol pathways. Pedigree analysis has shown a strong genetic componentin Type II diabetes (Kahn et al., Annu. Rev. Med. 47: 509–531,1996). Inaddition, obesity is also a major risk factor in Type II diabetes (Kahnet al., Annu. Rev. Med. 47: 509–531,1996). Genetic or obesity-induced(Hotamisligil et al., Science 259: 87–91, 1993; Lonnqvist et al., NatMed 1: 950–953, 1995) declines in a DAF-7-like signaling pathway couldunderlie the lack of response to insulin in Type II diabetes, just as inC. elegans daf-7 mutants cause metabolic defects very similar to daf-2mutants. The discovery that the DAF-7 and DAF-2 pathways convergeindicates that DAF-7 hormonal signals are defective in diabeticconditions (for example, Type II diabetes), and that administration ofhuman DAF-7 is useful for ameliorating the glucose intolerance,ketoacidosis, and atherosclerosis associated with diabetes. This isshown schematically in FIGS. 17, 18, and 23.

Whereas the DAF-7 TGF-β like and DAF-2 insulin-like signaling pathwaysconverge to control diapause and metabolism, only the DAF-2/AGE-1pathway has been implicated in reproductive adult stage longevitycontrol in the absense of dauer formation (Larsen et al., Genetics 139:1567–1583, 1995; Kenyon et al., Nature 366: 461–464, 1993; Dorman etal., Genetics 141: 1399–1406, 1995; and Morris et al., Nature 382:536–539, 1996). Both pathways control the longevity increase associatedwith dauer arrest, since dauer larvae live much longer than reproductiveC. elegans (Riddle, In: Caenorhabditis elegans II, D. Riddle, T.Blumenthal, B. Meyer, J. Priess, ed., Cold Spring Harbor Laboratory,Cold Spring Harbor, N.Y., 1997, pp. 739–768; Kenyon, op cit. pp.,791–813: Chayen and Bitensky, Practical Histochemistry, Chichester;N.Y.: Wiley, 1991. The distinction between DAF-7 and DAF-2 regulation oflongevity could also reflect a more profound regulation of metabolism bythe DAF-2 pathway than the DAF-7 pathway (FIG. 4). For example, based onprecedents from TGF-β signaling in other systems and analysis of thispathway in C. elegans, all of the known signaling output of the DAF-7TGF-β pathway are via downstream Smad transcriptional regulation(infra). Insulin signaling, and by extension, DAF-2 signaling, is moreramified: outputs from this receptor regulate sugar transport, metabolicenzyme activities, translation of mRNAs encoding these and otherenzymes, as well as transcription (White and Kahn, J. Biol. Chem. 269:1–4, 1994). We suggest that it is the regulatory output distinct to theDAF-2 pathway that controls longevity. Alternatively, TGF-β andinsulin-like signals may converge only during the L1 stage, whendiapause is regulated, and that after this stage, only DAF-2 signalingis necessary for normal metabolic control.

The involvement of insulin and TGF-β signaling in C. elegans diapausecontrol suggests that the homologous human pathways may similarlymediate response to famine. Just as environmental extremes can selectfor variation in the genetic pathways that regulate C. elegans dauerformation, famines and droughts in human history may have selected foranalogous variants in the human homolog of the daf genes. In fact,heterozygous mice carrying either the db or ob recessive diabetes genes,survive fasting about 20% longer than wild type controls (Coleman,Science 203: 663–665, 1979). The high frequency of Type II diabetes inmany human populations may be the legacy of such selections.

The DAF-3 Smad Protein Anatagonizes DAF-7 TGF-β Receptor Signaling inthe C. elegans Dauer Regulatory Pathway

In response to environmental signals C. elegans arrests development atthe anatomically and metabolically distinctive third-larval dauer stage(Riddle In: C. elegans N, D. L. Riddle, T. Blumenthal, B. J. Meyer, J.R. Priess, eds., Cold Spring Harbor Press, 1997, pp. 739–768). Pheromonesignal is transduced by chemosensory neurons (Bargmann and Horvitz,Science 251:1243, 1991) which couple to a TGF-β signaling pathway (Renet al., Science 274:1389, 1996; Schackwitz et al., Neuron 17:719, 1989),as well as an insulin-related signaling pathway (as discussed, infra) totrigger changes in the development of the many tissues remodeled indauer larvae (Riddle, supra). Mutations in daf-7 (a TGF-β homolog(Estevez et al., Nature 365:644, 1993)), daf-4 (a type II TGF-β receptor(Estevez et al., Nature 365:644, 1993)), daf-1 (a type I TGF-βreceptor), daf-8, and daf-14 (Smad homolog) cause constitutive arrest atthe dauer stage even in the absence of pheromone. These genes constitutea neuroendocrine signaling pathway that is active during non-dauerdevelopment: the DAF-7 TGF-β signal is produced by the sensory neuronASI during nondauer development, whereas daf-7 expression in this neuronis inhibited during dauer-inducing conditions (Ren, supra).

daf-7 and its receptors and Smad proteins are antagonists to daf-3. Thedauer constitute phenotypes of mutations in the daf-7 signaltransduction pathway genes (including putative null mutations) are fullysuppressed by mutations in daf-3. These genetic data indicate that inthe absence of daf-7 signaling, daf-3 acts to induce dauer arrest.

To discern the molecular basis of the DAF-3 function in this pathway, wedetermined the sequence and expression pattern of daf-3. Cosmids in thedaf-3 genetic region were assayed for gene activity by transformation.Cosmid B0217 partially complemented a daf-3 mutation, while othercosmids from the region did not (FIG. 5A). A subclone of B0217containing only the Smad homolog, but no other coding regions alsorescued daf-3. Our detection of mutations in the Smad homolog (seebelow) confirmed its assignment to daf-3. Analysis of daf-3 cDNAsrevealed that the gene was transcribed from fifteen exons and wasalternatively spliced upstream of the region conserved in Smad proteins.(FIG. 5B) The biological activity of these alternatively splicedisoforms is unknown. The nucleotide (SEQ ID NO: 11) and amino acidsequences (SEQ ID NO: 12) of DAF-3 are shown in FIGS. 11 and 12,respectively.

Thus far, the C. elegans DAF-3 Smad protein is most closely related insequence to DPC4, which is a putative cofactor for Smad1, Smad2, andSmad3 (Zhang et al., Nature, 383:168, 1996; Lagna et al., Nature,383:832, 1996; Savage et al., Proc. Natl. Acad. Sci., 93:790, 1996; Hahnet al., Science, 271:350 (1996). Smads have two conserved domains (Wranaet al., Trends Genet., 12:493, 1996). DAF-3 has these two domains;compared to its closest known relative DPC-4, daf-3 has 55% amino acididentity in domain I and 30% in domain II (FIG. 5C). However, DPC-4 isnot the mammalian DAF-3 homologue: C. elegans Sma-4, for example, ismore closely related to DPC-4 than DAF-3.

We identified three mutations in daf-3, all of which were isolated assuppressors of daf-7(e1372). mgDf90 is a homozygous viable deletion of15–90 kb that removes the entire Smad gene (FIG. 5A). mgDf90 wasidentified as a spontaneous mutation that suppressed daf-7 in the strainof GR1300 (daf-7 (e1372) 111; mut-6(st 702) unc-22 (St192) IV). Thus,suppression of the daf-7 dauer constitutive phenotype of daf-3 is daf-3null phenotype, demonstrating that wild-type DAF-3 acts antagonisticallyto signaling from the DAF-7 TGF-β pathway signaling. daf-3(mg125) anddaf-3(mg132) are missense mutations that alter conserved residues indomains 1 and 2 respectively (FIG. 5C). Most of the mutations detectedin other Smads localize to a 45 amino acid segment of domain II (Wranaet al., Trends in Genet. 12:493, 1996). Clustering of mutations isobserved even in DPC4, for which homozygous null mutations have beenidentified (Hahn et al., Science 271:350, 1996), so the clustering isunlikely to be due to selection for non-null mutations. This hotspotregion was sequenced in nine daf-3 alleles, and no mutations weredetected. This difference in mutation location may be a simplestatistical anomaly, or may indicate functional differences betweenDAF-3 and other Smad proteins, consistent with the fact that DAF-3 isantagonized, rather than activated, by an upstream TGF-β molecule.

To determine where DAF-3 may function in control of dauer formation, weexamined the expression pattern of a functional daf-3/Green FluorescentProtein (GFP) fusion gene. This was accomplished by replacing aAvrII/SacI fragment from pGP8 with a PCR product in which severalrestriction sites were inserted after the last codon of daf-3 before thestop codon. A GFP/unc-54 3′ end PCR product from pPD95.81 was clonedinto the 3′ restriction sites to produce pGP19. This DAF-3/GFP fusionpartially rescues a daf-3 mutant (FIG. 7). GFP fluorescence thereforeindicates the functional location of DAF-3. DAF-7 signaling from the ASIneuron begins during the L1 stage, and neuron ablations anddauer-formation assays in various environmental conditions indicate thatthe signal for dauer formation is also received during the first twolarval stages (Ren et al., Science 274:1389, 1996, Schackwitz et al.,Neuron 17:719, 1996; Bargmann and Horvitz, Science 251:1243, 1991;Golden and Riddle, Developmental Biology 102:368, 1984; Swanson andRiddle, Developmental Biology 84:27, 1981). Therefore, we mostextensively examined L1 larvae.

Almost every transgenic animal showed strong daf-3/GFP expression inhead neurons (FIG. 6A), the ventral nerve cord (both cell bodies andprocesses, see FIG. 6B), the intestinal cells (FIG. 6C), especially themembrane adjacent to the intestinal lumen, the tail hypodermis, and tailneurons. For all GFP scoring, animals were grown at 25–26° C. Forscoring of DAF-3/GFP in wild-type and in dauer constitutive mutantbackgrounds, three or more lines were scored in each case. A largenumber of animals were surveyed to determine the expression pattern, andat least 30 animals were scored head-to-tail, and expression was talliedfor each tissue. About half of the transgenic animals have weakexpression in V blast cells, P blast cells, hyp7 hypodermal cells, andthe pharynx. The weak expression impedes cell identification, but themain body of the pharynx is filled, implying expression in pharyngealmuscle (FIG. 6A). Expression is rarely detected in dorsal body wallmuscle. The expression pattern in older larvae and adults is similar tothat of L1 animals. In addition, DAF-3/GFP is expressed in the distaltip cells and in their precursors, Z1.a and Z4.p, throughout development(FIG. 6D, FIG. 8). DAF-3/GFP is also strongly expressed in unidentifiedvulval cells. In wild-type embryos of 200–400 cells, DAF-3/GFP isexpressed uniformly thoughout the embryo (FIG. 6E). Under the conditionsof the experiment, which promote reproductive growth, the subcellularlocalization of the DAF-3/GFP protein is mainly cytoplasmic (FIGS. 6B–E,and see below).

Because DAF-3 activity may be regulated by the DAF-1 and DAF-4 TGF-βreceptors, we examined the expression of a DAF-4/GFP fusion in wild-type(FIGS. 6A–6G). This construct complements a daf-4 mutant. A 10 kb SalIfragment from cosmid CO5D2 contains 3 kb of sequence upstream of thedaf-4 transcriptional start, and all of the daf-4 coding region exceptcodons for the last fourteen residues of daf-4. This fragment wassubcloned into the SalI site of the GFP plasmid TU#61 (Chalfie et al.,Science 263: 802–805, 1994). This plasmid was injected into thedaf-4(m72) strain to test the fusion for DAF-4 activity. More than 95%of the transgenic animals were rescued for the dauer-constitutive andsmall phenotypes of daf-4(m72), indicating that the fusion has robustDAF-4 activity. The pattern of DAF-4/GFP expression is similar to thatof daf-3/GFP, except that DAF-4/GFP is localized to membranes,consistent with its role as a receptor. DAF-4/GFP is expressed morestrongly in the pharynx (FIGS. 6F–G), and more weakly in the ventralnerve cord cell bodies and the body hypodermis. Expression of DAF-4/GFPin wild-type animals is detected later than DAF-3/GFP. DAF-4/GFP isfirst detectable at late embryogenesis when the embryo resembles an L1larva. The DAF-4/GFP construct contains an older version of GFP than inDAF-3/GFP; in the older version, the chromophore takes longer to mature.To verify that the difference in embryonic expression of DAF-4/GFP andDAF-3/GFP is not an artefact of the slower maturation time in the daf-4strain, we used anti-GFP antibodies to assay GFP. These antibodiesshould recognize the two forms of GFP equally well. We found that theantibodies recapitulated the results with direct GFP fluorescence:DAF-3/GFP is expressed in early embryos; DAF-4/GFP is not. DAF-4/GFP isalso not expressed in membrane surrounding the intestinal lumen, unlikeDAF-3/GFP.

The combination of the DAF-3 and DAF-4 expression patterns suggests thatthese genes act in target tissues to transduce pheromone-regulated DAF-7neuroendocrine signals. The early expression of DAF-3 in embryos is alsoconsistent with a model that DAF-3 acts during embryonic development,for example, to mediate the development of neuronal pathways that emitneuroendocrine signals that antagonize DAF-7 TGF-β signaling during theL1 stage. However our data indicates that DAF-3 functions in transducingenvironmental signals during the L1 and L2 stages. This is supported bythe following observations. (1) DAF-7 TGF-β signal from ASI neuronsoccurs during the L1 and L2 stages and is repressed by dauer-inducingenvironmental conditions. (2) Expression of the DAF-4 type II receptorbegins in very late embryogenesis. (3) Expression patterns of DAF-3 andDAF-4 are coincident in most of the tissues remodeled during dauermorphogenesis. For example, the cuticle secreted by the hypodermis ismodified, the pharynx is slimmed, and the lumen of the intestine is lessconvoluted. In addition, somatic gonad development is arrested indauers, and the distal tip cell, in which DAF-3 is expressed, is animportant regulator of that development (Kimble, Developmental Biology87:286, 1981). In addition, the intestine and hypodermis of dauer larvaecontain large fat stores indicative of a metabolic shift to fat storage.The expression of both the DAF-4 TGF-β family receptor kinase and theDAF-3 Smad protein in these target tissues is consistent with a modelthat the DAF-7 neuroendocrine signal from the ASI neuron is receiveddirectly by these tissues during non dauer development. In addition, theobservation that DAF-4 and DAF-3 are expressed in many of the same cellsis consistent with a model that DAF-4 signaling to downstream Smads(DAF-8 and DAF-14 are likely candidates) directly regulates DAF-3 geneactivity. The TGF-β regulated nuclear localization and transcriptionalactivation of some Smad proteins suggests that DAF-3 might induce thedauer-specific changes by activating transcription in target tissues ofgenes required for dauer formation or repressing transcription of genesnecessary for nondauer growth.

Smad1 and Smad2 relocalize to become predominantly nuclear when theupstream TGF-β signaling pathways are activated (Baker and Harland,Genes and Development 10: 1880, 1996; Hoodless et al., Cell 85:489,1996; Liu et al., Nature 381:620, 1996; Macias-Silva et al., Cell87:1215, 1996). In wild-type, DAF-3/GFP is primarily, although notexclusively, cytoplasmic. DAF-3/GFP subcellular distribution wasexamined in head neurons in the vicinity of ASI (the cell that producesthe DAF-7 signal), as well as in intestinal cells. DAF-3/GFP waspredominantly cytoplasmic in all animals. However, in all animals, dimGFP fluorescence was observed in the nucleus of some of the cells withbright fluoresence, and in approximately twenty-five percent of theanimals, equivalent DAF-3/GFP levels in the nucleus and cytoplasm hasobserved in one or more cells.

Because DAF-3 is antagonized by the other members of the DAF-7 TGF-βpathway, we expect that DAF-3 is active (and perhaps localized to thenucleus) when these genes are inactive. We therefore observed thesubcellular localization of the full-length DAF-3/GFP fusion protein inthe head neurons, tail neurons, and intestine of dauer-constitutivemutant L1 worms, when DAF-3 gene activity is predicted to be highest. InDAF-1(m402), daf-4(m72), daf-7(m62), daf-8(sa233), and daf-14(m77)mutants, DAF-3/GFP was predominantly cytoplasmic, although, as inwild-type, cells were seen with some GFP in the nucleus. In threedaf-4(m72) mutant lines, DAF-3/GFP was localized to the nucleus morethan in wild-type lines. When these strains were crossed to wild-type,the increased nuclear localization was seen in both the daf-4 andwild-type segregants. Thus the increased nuclear GFP was a property ofthe array, rather than of daf-4. Even in the neurons nearest to ASI,where the DAF-7 signal should be strongest, no change in DAF-3/GFPsubcellular localization was detected. The DAF-3/GFP fusion protein ispredominantly cytoplasmic in L1 and L2 stages of larvae induced to formdauers by environmental conditions or by mutations in the insulinreceptor pathway gene daf-2, rather than by mutations in the DAF-7signaling pathway mutants (data not shown). The tissue-specificexpression pattern of DAF-3/GFP was unaltered in these mutantbackgrounds (data not shown).

The finding that DAF-3/GFP subcellular localization is not stronglyresponsive to DAF-7 signaling defects or to dauer-inducing environmentalconditions does not rule out a role for DAF-3 in the nucleus in dauerformation. Even though we detect no change in DAF-3/GFP subcellularlocalization, we do detect some DAF-3/GFP in nuclei, and a minor changein nuclear localization or a change in activity due to phosphorylationstate may couple DAF-3 to DAF-7 signaling. In fact, the subcellularlocalization of Drosophila MAD protein is not detectably altered inwild-type when receptor signaling to MAD occurs; relocalization is seenonly if the DPP ligand is drastically overexpressed. It is unlikely thata set of undiscovered TGF-β receptors regulates DAF-3. The C. elegansgenome sequence is 90% complete, and there is only one candidate TGF-βreceptor gene other than daf-1 and daf-4. If this receptor were apositive regulator of DAF-3, mutants would be expected to, like daf-3mutants, suppress daf-7 mutants. This receptor acts in a signalingpathway distinct from DAF-3, and it is not a suppressor of daf-7.

The implication from Smad homology that DAF-3 is active in the nucleusis supported by two additional observations. First, DAF-3/GFP isassociated with chromosomes in intestinal cells during mitosis. Thesecells divide at the end of the L1 stage, and antibody staining withanti-GFP antibodies and anti-α-tubulin antibodies reveals that DAF-3/GFPis found associated with DNA between the spindles during mitosis (FIG.8A). We see DAF-3 GFP co-localized with DAPI from prophase to lateanaphase. DAF-3/GFP was associated with nuclei in prophase by thefollowing criteria. The spindles were present on either side of thenucleus, but the nucleus has not completely broken down. In particular,an indistinct nucleolus was present. DAF-3/GFP continues to co-localizewith DAPI until the chromosomes have separated to the normal distance bywhich nuclei are separated in the intestine, implying continuedassociation until telophase. At this point in mitosis, DAF-3/GFP fadesand becomes undectectable before the nuclei reform the nuclear envelopeand nucleolus. Thus, DAF-3 can, indirectly or directly, bind DNA,consistent with the hypothesis that it is a transcriptional activatorthat acts in the nucleus. DAF-3 is not predicted from its mutantphenotype to have a role in mitosis. It is possible that the brighterGFP on mitotic chromosomes is due to increased access to DNA due to thebreakdown of the nuclear envelope. The second indication of DAF-3function in the nucleus is our examination of a truncated DAF-3/GFPfusion that is missing most of conserved domain II. The truncatedconstruct pGP7 consists of 8 kb of daf-3 fused to GFP. An 8 kb EcoRIfragment from B0217 was cloned into the EcoR1 site of pBluescript SK(−).A Pvul/Sall fragment of this subclone was ligated to a Pvul/Sallfragment from the GFP vector pPD95.81. The resulting plasmid contains˜2.5 kb of sequence upstream of the 5′-most exon of daf-3 and codingregion through the first 58 amino acid residues of domain II. Theremaining 175 amino acids of daf-3 and the 3′ noncoding region arereplaced with GFP and the unc-54 3′ end. Three transgenic lines wereisolated, and all had a similar phenotype. This fusion proteininterferes with dauer induction; like a daf-3 loss-of-function mutant,it suppresses mutations in daf-7 (FIG. 7). This truncated protein ispredominantly nuclear, suggesting that it represses dauer formation byacting in the nucleus (FIG. 8B). This result implies that wild-typeDAF-3 also has a function in the nucleus. The full-length DAF-3/GFPconstruct also suppresses mutations in daf-7, as does a full-lengthDAF-3 construct without GFP (FIG. 7). This suppression indicates thatoverexpression of DAF-3 in the cytoplasm has dominant-negative activity,perhaps due to interference with DAF-3 interactions with receptors orcofactors such as other Smads.

The constitutive nuclear localization of truncated DAF-3/GFP fusion genemissing part of domain II suggests that control of Smad localization iscomplex. A Smad2 construct containing only the conserved domain II ofthe protein is constitutively nuclear, leading to the suggestion thatthe C-terminus is an effector domain, and the N-terminus tethers theprotein in the cytoplasm (Baker and Harland, Genes and Development10:1880, 1996; Hoodless et al., Cell 85:489, 1996; Liu et al., Nature381:620, 1996; and Macias-Silva et al., Cell 87:1215, 1996). Ourconstruct, in which the N-terminus is intact, is nuclear. Perhaps bothdomains provide tethering in the cytoplasm, and any disruption leads tonuclear entry. Alternatively, entry may be differently regulated forDAF-3 and Smad2. Significantly, Smad2, like Smad1 and Smad3 has an SSXSmotif at the C terminus (Zhang et al., Nature 383:168, 1996; Lagna etal., Nature 383:832, 1996; Savage et al., PNAS 93:790; Baker andHarland, Genes and Development 10:1880, 1996; Hoodless et al., Cell85:489, 1996; Liu et al., Nature 381:620, 1996; Macias-Silva et al.,Cell 87:1215, 1996; and Graf et al., Cell 85:479, 1996); this motif is asubstrate for phosphorylation and required for nuclear localization ofSmad2 (Baker and Harland, Genes and Development 10:1880, 1996; Hoodlesset al., Cell 85:489, 1996; Liu et al., Nature 381:620, 1996; andMacias-Silva et al., Cell 87:1215, 1996). DAF-3 has a single serine inthe C terminal region, and DPC4 has no serines at this location.

We propose a model for the TGF-β pathway in dauer formation (FIGS.9A–B). The DAF-7 TGF-β ligand, which is produced by the ASI sensoryneuron in conditions that induce reproductive organ (Ren et al., Science274:1389, 1996; Schakwitz et al., Neuron 17:719, 1996), binds to theDAF-1/DAF-4 receptor kinases on target tissues. These receptor kinasesthen phosphorylate the Smads DAF-8 and/or DAF-14, analogous to thephosphorylation and activation of Smad1, Smad2, and Smad3 (Zhang et al.,Nature 383:168, 1996; Lagna et al., Nature 383:832, 1996; Savage et al.,PNAS 93:790, 1996). We propose that DAF-3 functions like its closesthomolog, DPC4, which dimerizes with phosphorylated Smad1 and Smad2, evenunder conditions that do not lead to detectable DPC4 phosphorylation(Zhang et al., Nature 383:168, 1996; Lagna et al., Nature 383:832, 1996;and Savage et al., PNAS 93:790). We suggest that DAF-3 formsdauer-inducing homodimers in the absence of DAF-7 signaling (FIGS. 9A–B)that are disrupted when DAF-3 heterodimerizes with a phosphorylatedDAF-8 and/or DAF-14 (FIG. 9B). Because daf-8 and daf-14 are onlypartially redundant (Riddle et al., Nature 290:668, 1981; Vowels andThomas, Genetics 130:105, 1992; and Thomas et al., Genetics 134:1105,1993), each is likely to perform a unique function in dauer formation.Thus, DAF-3/DAF-8 dimers are proposed to have different activity fromDAF-3/DAF-14. Perhaps each activates a subset of genes required fordauer formation. The formation of DAF-8/DAF-3 and/or DAF-14/DAF-3heterodimers antagonizes dauer induction by the DAF-3/DAF-3 homodimer. Adaf-8(sa233); daf-14(m77); daf-3(mgDf90) triple mutant can form somedauers in dauer-inducing conditions (data not shown); we suggest thatactivity of the Daf-2 pathway may induce dauer in this mutantbackground.

The dauer genetic pathway represents a neuroendocrine pathway forcontrol of a diapause arrest and its associated shifts in metabolism andrates of senescence (Ren et al., Science 274:1389, 1996; Schackwitz etal., Neuron 17:719, 1996; and Georgi et al., Cell 61:635, 1990).Similarly, activins, members of the TGF-β family, were originallyidentified based on their neuroendocrine regulatory activity, forexample, in regulation of gonadotropin signaling (Vale et al., inPeptide Growth Factors and Their Receptors, Sporn and Roberts, Eds.,Springer-Verlag, Heidelberg, 1990). The DAF-7 signal is not the onlysignal that is necessary for reproductive development. Because mutationsin the DAF-7 TGF-β pathway and in the DAF-2 insulin-like signalingpathway cause the same dauer arrest phenotypes, we propose that both theDAF-7 TGF-β signals and the DAF-2 insulin-like signals are necessary forreproductive development. The involvement of an insulin-like signalingpathway in diapause with its associated metabolic shifts is consistentwith metabolic regulation by insulin in vertebrates. Genetic experimentsindicate that these pathways act in parallel (Riddle et al., Nature290:668, 1981; Vowels and Thomas, Genetics 130:105, 1992; and Thomas etal., Genetics 134:1105, 1993). In particular, daf-3 mutants efficientlysuppress daf-7 mutants, but not daf-2 mutants, and daf-16 mutantsefficiently suppress daf-2 mutants, but poorly suppress daf-7 mutants.It is not yet clear whether these two signaling pathways coverage ontarget tissues or in other regulatory (e.g., hormone secreting) cells.However, the expression of the DAF-7 receptor pathway genes and theDAF-16 gene in essentially all target tissues suggests that the TGF-βand insulin pathways act there, and therefore that integration mustoccur there. Thus, we suggest in FIGS. 9A and 9B that the DAF-2 pathwayconverges on DAF-3/DAF-8DAF-1 Smad signaling to regulate metabolic geneexpression in target tissues.

The integration of insulin-like and TGF-β signals in metabolic controlhas important implications for the molecular basis of diabetes. Forexample, these converging pathways for dauer control suggest that inhuman metabolic control both a DAF-7-like signal and insulin may benecessary for full metabolic control. Thus, declines in signaling fromthe human homolog of DAF-7 could underlie the insulin resistanceassociated with Type II diabetes. In fact the dauer pheromone has beenreported to be a fatty acid and to cause down-regulation of DAF-7expression (Ren et al., supra). Thus pheromone regulation of metabolismmay be related to mammalian obesity induced diabetes, and a humanmutation in DAF-7 or its receptors is expected to contribute to adiabetic condition, just like mutations in the insulin receptor. Inaddition if obesity or age or both cause human DAF-7 to decline, e.g.,under high leptin conditions, such a result would explain lateonset/obesity related diabetes.

Converging Transcriptional Outputs of the Insulin and DAF-7 EndocrineSignals

Further support for the view that insulin-like and DAF-7 neuroendocrinesignals regulate common transcriptional targets via the DAF-16 Forkheadprotein and the DAF-8, DAF-14, and DAF-3 Smad proteins, respectively,comes from the following experiments. First, we have shown that the a 30base element in the myosin 2 promoter, previously shown to bind to DAF-3and be responsive to DAF-7 signaling, is also responsive to DAF-2insulin like signaling (Okkema, Development, 1994, 120(8):2175–86). Thiselement has the following sequence (SEQ ID NO: 210):TCTCGTTGTTTGCCGTCGGATGTCTGCC. The bolded nucleotide positions areconserved in the Xenopus activin response element. Specifically, a GFPfusion of this element (multimerized 6×) expresses 24 units offluorescence in wild type, but less than 4 units in a daf-4 TGF-βsignaling mutant or in a daf-2 insulin-like signaling mutant. Thisrepression of expression by lack of neuroendocrine input is relieved bymutations in daf-3 in the case of the daf-4 mutant and daf-16 in thecase of the daf-2 mutant. The daf-4; daf-3 double mutant expresses 12units of GFP fluorescence and the daf-2; daf-16 double mutant expresses18 units of GFP fluorescence. These data strongly support the model thatDAF-16 and DAF-3 bind to the same element in the myosin promoter. Thisis biologically relevant since the pharynx is smaller in dauer arrestedanimals, consistent with lower pharyngeal myosin expression in animalswith defective DAF-7 or DAF-2 signaling.

Serotinergic Input to the Dauer Pathway

We have further shown that mutants completely lacking in serotonin havedefects in metabolic control. Specifically we have knocked out theserotonin synthesis gene, tryptophan hydroxylase, cod-5, by directedmutagenesis. Cod-5 is the aromatic amino acid hydroxylase thatsynthesises serotonin from the precursor L tryptophan (FIG. 42). It isthe rate determining step in the synthesis of serotonin, and we haveshown that it is only transcribed in the serotinergic neurons of C.elegans.

Our deletion mutant deletes most of the cod-5 gene and causes aframeshift in the remaining coding region (FIG. 43). This mutant makesno serotonin as measured with antiserotonin antibody staining. Thepromoter of cod-5 fused to GFP displays all of the serotinergic neuronsof C. elegans, NSM, HSN, ADF, RIH (but not VC4 and VC5 which probablyuptake 5HT from surrounding serotinergic neurons).

The cod-5 null mutant has a number of behavioral abnormalities,including egg laying defects, fertility declines, thermal regulationdefects, and hyperactive movement, but most dramatic is that up to halfof the mutant animals arrest at the dauer stage and accumulate largeamounts of fat. This is quite similar to the regulation of feeding,appetite, and metabolism by serotonin in vertebrates. The behavior ofcod-5 mutants also shows the hallmarks of defects in DAF-7 signaling:the cod-5 mutant animals tend to cluster at the edge of a lawn ofbacteria, as if they are attracted to each other and repelled by thebacteria. This type of behavior is also seen in an NPY receptor mutant,bor-1. It is possible that DAF-7 normally regulates the secretion of theNPY like ligand of bor-1, and 5HT regulates DAF-7. This would explainthe dauer arrest and bordering behavior of cod-5 mutants, that it actshigh in the pathway of DAF-7.

5HT production is normally under feeding and temperature control: wildtype C. elegans makes almost undetectable levels of 5HT when starved andmakes lower amounts at low temperature. We believe that 5HT receptorsare expressed on particular regulatory neurons that also express orrespond to the DAF-7 or DAF-2 signals, either as ligands or receptors.5HT regulation of metabolism may occur via the DAF-7 pathway or theDAF-2 pathway, for example, by regulating expression of DAF-7,expression or secretion of the DAF-2 ligands, or signaling from thereceptors. Moreover, given that cod-5 mutations induce the samebehavioral changes (that is, crowding at the edge of food) as daf-7mutants (in distinction from daf-11 or daf-2 pathway mutants), webelieve that there is 5HT input to the daf-7 pathway.

Our discovery of 5HT input to C. elegans metabolic control is importantbecause it may reveal the mechanism by which drugs like dexfenfluramineand fluoxetine control weight in humans (Weiser et al., J ClinPharmacol, 1997, 37(6):453–73). For example, if 5HT input to wormmetabolic control is via the DAF-7 signaling system, the mechanism ofaction of serotinergic signals in metabolic control in mammals may bevia serotonin modulation of expression or secretion of the mammalianDAF-7 homologue.

In addition, the cod-5 promoter-GFP fusion is valuable for its abilityto display serotinergic neurons, for example, for screens of mutantsthat fail to generate serotinergic neurons or screens for mutants thatgenerate ectopic serotinergic neurons. Such a promoter fusion, forexample, facilitates the identification of the neural pathway for thegeneration of 5HT neurons. In fact, the transcription factor unc-86 hasalready been identified as part of that pathway. Unc-86 mutants cause alack of serotonin synthesis, due to loss of cod-5 expression in allserotinergic neurons except ADF, and we have shown that the accumulationof serotonin in the NSM in an unc-86 mutant is due to reuptake of 5HT,presumably from the ADF site of serotonin synthesis. Prozac, a reuptakeinhibitor, causes 5HT accumulation in the NSM to disappear in unc-86mutants.

Cloning Mammalian DAF Sequences

Based on our isolation of novel nematode DAF cDNAs, the isolation ofmammalian DAF nucleic acid sequences, including human DAF sequences, ismade possible using the sequences described herein and standardtechniques. In particular, using all or a portion of a nematode DAFsequence, one may readily design oligonucleotide probes, includingdegenerate oligonucleotide probes (i.e., a mixture of all possiblecoding sequences for a given amino acid sequence). Theseoligonucleotides may be based upon the sequence of either strand of theDNA.

Exemplary probes or primers for isolating mammalian DAF sequencespreferably correspond to conserved blocks of amino acids, for example,conserved DAF motifs. Exemplary motifs are as follows:

DAF-2  (tyrosine kinase domain) (SEQ ID NO: 33) 1242KFHEWAAQICDGMAYLESLKFCHRDLAARNCMINRDETVKIGDFGMARDLFYHDYYKPSGKRMMPVRWMSPESLKDGKFDSKSDVWSFGVVLYEMVTLGAQPYIGLSNDEVLNYIGMARKVIKKPEC 1368 DAF-2  (ligand bindingdomain) (SEQ ID NO: 34) 242 NTTCQKSCAYDRLLPTKEIGPGCDANGDRCHDQCVGGCERVNDATACHACKNVYTIKGKCIEKCDAHLYLLLQRRCVTREQCLQLNPVLSNKTVPIKATAGLCSDKCPDGYQINPDDHRECRKCVGKCELVC 372 DAF-2  (67 amino acidmotif) (SEQ ID NO: 79) 1158 AIKINVDDPASTENLNYLMEANIMKNFKTNFIVQLYGVISTVQPAMYVMEMMDLGNLRDYLRSKRED  1224 DAF-2  (54 amino acid motif) (SEQ ID NO:80) 1362 VIKKPECCENYWYKVMKMCWRYSPRDRPTFLQLVHLLAAEASPE FRDLSFVLTD  1415DAF-2  (69 amino acid motif) (SEQ ID NO: 81) 404KQDSGMASELKDIFANIHTITGYLLVRQSSPFISLNMFRNLRRIEAKSLFRNLYAITVFENPNLKKLFD  472 DAF-2  (52 amino acid motif) (SEQ ID NO:82) 98 FPHLREITGTLLVFETEGLVDLRKIFPNLRVIGGRSLIQIIYAL IIYRNPDLE  149DAF-2  (46 amino acid motif) (SEQ ID NO: 83) 149EIGLDKLSVIRNGGVRIIDNRKLCYTKTIDWKHLITSSINDVVV DN  194 DAF-2  (36 aminoacid motif) (SEQ ID NO: 84) 1112YNADDWELRQDDVVLGQQCGEGSFGKVYLGTGNNVV  1147 DAF-3  (Smad Domain I) (SEQID NO: 35) 240 FDQKACESLVKKLKDKKNDLQNLIDVVLSKGTKYTGCITIPRTLDGRLQVHGRKGFPHVVYGKLWRFNEMTKNETRIIVDHCKHAFEM KSDMVCVNPYHYEIVI  342DAF-3  (Smad Domain II) (SEQ ID NO: 36) 690NRYSLGLEPNPIREPVAFKVRKAIVDGIRFSYKKDGSVWLQNRMKYPVFVTSGYLDEQSGGLKKDKVHKVYGCASIKTF  768 DAF-3  (79 amino acid motif)(SEQ ID NO: 85) 819 DSLAKYCCVRVSFCKGFGEAYPER  842 DAF-16 (forkhead DNAbinding domain) (SEQ ID NO: 37) 727KKTTTRRNAWGNMSYAELITTAIMASPEKRLTLAQVYEWMVQNVPYFRDKGDSNSSAGWKNSIRHNLSLHSRFMRIQNEGAGKSSWWV INPDAKPGMNPRRTRERS  1044DAF-16 (103 amino acid motif) (SEQ ID NO: 54) 242KKTTTRRNAWGNMSYAELITTAIMASPEKRLTLAQVYEWMVQNVPYFRDKGDSNSSAGWKNSIRHNLSLHSRFMRIQNEGAGKSSWWV INPDAKPGMNPRRTR  344 DAF-16(41 amino acid motif) (SEQ ID NO: 55) 137TFMNTPDDVMMNDDMEPIPRDRCNTWPMRRPQLEPPLNSSP 177 DAF-16 (109 amino acidmotif) (SEQ ID NO: 56) 236 DDTVSGKKTTTRRNAWGNMSYAELITTAIMASPEKRLTLAQVYEWMVQNVPYFRDKGDSNSSAGWKNSIRHNLSLLISRFMRIQNEGA GKSSWWVINPDAKPGMNPRRTR  344DAF-16 (98 amino acid motif) (SEQ ID NO: 58) 372KPNPWGEESYSDIIAKALESAPDGRLKLNELYQWFSDNIPYFGERSSPEEAAGWKNSLRHNLSLHSRFMRIQNEGAGKSSWWVIINPD AKPGMNPRRTR  469Using such motifs, mammalian DAF-2, DAF-3, and DAF-16 genes may beisolated from sequence databases (for example, by the use of standardprograms such as Pileup). Alternatively, such sequences may be used todesign degenerate oligonucleotide probes to probe large genomic or cDNAlibraries directly. General methods for designing and preparing suchprobes are provided, for example, in Ausubel et al., Current Protocolsin Molecular Biology, 1996, Wiley & Sons, New York, N.Y.; and Guide toMolecular Cloning Techniques, 1987, S. L. Berger and A. R. Kimmel, eds.,Academic Press, New York. These oligonucleotides are useful for DAF geneisolation, either through their use as probes for hybridizing to DAFcomplementary sequences or as primers for various polymerase chainreaction (PCR) cloning strategies. If a PCR approach is utilized, theprimers are optionally designed to allow cloning of the amplifiedproduct into a suitable vector. PCR is particularly useful for screeningcDNA libraries from rare tissue types.

Hybridization techniques and procedures are well known to those skilledin the art and are described, for example, in Ausubel et al., supra, andGuide to Molecular Cloning Techniques, supra. If desired, a combinationof different oligonucleotide probes may be used for the screening of therecombinant DNA library. The oligonucleotides are, for example, labelledwith ³²P using methods known in the art, and the detectably-labelledoligonucleotides are used to probe filter replicas from a recombinantDNA library. Recombinant DNA libraries (for example, human cDNAlibraries, such as hypothalamus- or pancreas-derived cDNA libraries,particularly for DAF-2 and DAF-7 cDNAs) may be prepared according tomethods well known in the art, for example, as described in Ausubel etal., supra, or may be obtained from commercial sources.

For detection or isolation of closely related DAF sequences, highstringency hybridization conditions may be employed; such conditionsinclude hybridization at about 42° C. and about 50% formamide; a firstwash at about 65° C., about 2× SSC, and 1% SDS; followed by a secondwash at about 65° C. and about 0.1% SDS, 1× SSC. Lower stringencyconditions for detecting DAF genes having less sequence identity to thenematode DAF genes described herein include, for example, hybridizationat about 42° C. in the absence of formamide; a first wash at about 42°C., about 6× SSC, and about 1% SDS; and a second wash at about 50° C.,about 6× SSC, and about 1% SDS.

As discussed above, DAF-specific oligonucleotides may also be used asprimers in PCR cloning strategies. Such PCR methods are well known inthe art and are described, for example, in PCR Technology, H. A. Erlich,ed., Stockton Press, London, 1989; PCR Protocols: A Guide to Methods andApplications, M. A. Innis, D. H. Gelfand, J. J. Sninsky, and T. J.White, eds., Academic Press, Inc., New York, 1990; and Ausubel et al.,supra. Again, sequences corresponding to conserved regions in a DAFsequence (for example, those regions described above) are preferred foruse in isolating mammalian DAF sequences. Such probes may be used toscreen cDNA as well as genomic DNA libraries.

Sequences obtained are then examined (for example, using the Pileupprogram) to identify those sequences having the highest amino acidsequence identity to the C. elegans sequence, particularly in or betweenconserved DAF domains (for example, those domains described above). Inone particular example, the human FKHR, FKHRL1, and AFX genes are 10³³more closely related to the DAF-16 forkhead domain than the next mostclosely related forkhead domain protein, making FKHR, FKHRL1, and AFXcandidates for mammalian DAF-16 genes.

Following isolation of such candidate genes by sequence homology, thegenes are then tested for their ability to functionally complement a dafmutation. This is most readily assayed by transformation of the sequenceinto a C. elegans strain having an appropriate mutant background.Exemplary C. elegans transformation techniques are described, forexample, in Mello et al., EMBO J. 10: 3959–3970, 1991, and assays forDAF-2, DAF-3, and DAF-16 polypeptide function are described herein. Tobe considered useful in the invention, a mammalian sequence need notfully complement a C. elegans defect, but must provide a detectablelevel of functional complementation.

The DAF, AGE, or AKT gene homologue identified as above, may alsocomplement or alter the metabolic phenotypes of a mammalian cell line.

For example, addition of DAF-7, TGF-β-like growth factor to an insulinresponsive cell line (e.g., the 3T3-L1 cell line) may accentuate insulinresponsiveness. Similarly genetic transformation of such a cell linewith wild type or dominantly activated versions of a DAF, AGE, or AKTgene may alter metabolism. Such perturbations of metabolic control arestringent tests of candidate genes as DAF, AGE, or AKT homologues.

In addition, if that mammalian candidate homologue acts in a metaboliccontrol pathway, and is expressed in similar metabolic control tissues(liver, adipose), it is likely to function homologously to DAF proteinsfrom C. elegans. Addition of a wild type or activated DAF, AKT, or AGEprotein (for example by VP16 activation of the DAF-3 or DAF-16transcription factors) can confer on cell lines altered metabolicphenotypes. Thus supplying daf, age, or akt gene activity to such a cellline can alter its metabolism. This is one explemplary test ofhomologous DAF function in metabolic control.

DAF Polypeptide Expression

In general, DAF polypeptides according to the invention may be producedby transformation of a suitable host cell with all or part ofDAF-encoding cDNA fragment (e.g., one of the cDNAs described herein orisolated as described above) in a suitable expression vehicle.

Those skilled in the field of molecular biology will understand that anyof a wide variety of expression systems may be used to provide therecombinant protein. The precise host cell used is not critical to theinvention. The DAF polypeptide may be produced in a prokaryotic host(e.g., E. coli) or in a eukaryotic host (e.g., Saccharomyces cerevisiae,insect cells, e.g., Sf9 or Sf21 cells, or mammalian cells, e.g., COS 1,NIH 3T3, or HeLa cells). Such cells are available from a wide range ofsources (e.g., the American Type Culture Collection, Rockland, Md.;also, see, e.g., Ausubel et al., supra). The method of transformation ortransfection and the choice of expression vehicle will depend on thehost system selected. Transformation and transfection methods aredescribed, e.g., in Ausubel et al. (supra); expression vehicles may bechosen from those provided, e.g., in Cloning Vectors: A LaboratoryManual (P. H. Pouwels et al., 1985, Supp. 1987).

One preferred expression system is the baculovirus system (using, forexample, Sf9 cells and the method of Ausubel et al., supra). Anotherbaculovirus system makes use of the vector pBacPAK9 and is availablefrom Clontech (Palo Alto, Calif.).

Alternatively, an DAF polypeptide is produced in a mammalian system, forexample, by a stably-transfected mammalian cell line. A number ofvectors suitable for stable transfection of mammalian cells areavailable to the public, e.g., see Pouwels et al. (supra); methods forconstructing such cell lines are also publicly available, e.g., inAusubel et al. (supra). In one example, cDNA encoding the DAF protein iscloned into an expression vector which includes the dihydrofolatereductase (DHFR) gene. Integration of the plasmid and, therefore, theDAF protein-encoding gene into the host cell chromosome is selected forby inclusion of 0.01–300 μM methotrexate in the cell culture medium (asdescribed in Ausubel et al., supra). This dominant selection may beaccomplished in most cell types. Recombinant protein expression may beincreased by DIFR-mediated amplification of the transfected gene.Methods for selecting cell lines bearing gene amplifications aredescribed in Ausubel et al. (supra); such methods generally involveextended culture in medium containing gradually increasing levels ofmethotrexate. DIFR-containing expression vectors commonly used for thispurpose include pCVSEII-DHFR and pAdD26SV(A) (described in Ausubel etal., supra). Any of the host cells described above or, preferably, aDHFR-deficient CHO cell line (e.g., CHO DHFR⁻ cells, ATCC Accession No.CRL9096) are among the host cells preferred for DHFR selection of astably-transfected cell line or DHFR-mediated gene amplification.

In yet other alternative approaches, the DAF polypeptide is produced invivo or, preferably, in vitro using a T7 system (see, for example,Ausubel et al., supra, or other standard techniques).

Once the recombinant DAF protein is expressed, it is isolated, e.g.,using affinity chromatography. In one example, an anti-DAF proteinantibody (e.g., produced as described herein) may be attached to acolumn and used to isolate the DAF protein. Lysis and fractionation ofDAF protein-harboring cells prior to affinity chromatography may beperformed by standard methods (see, e.g., Ausubel et al., supra).

Once isolated, the recombinant protein can, if desired, be furtherpurified, e.g., by high performance liquid chromatography (see, e.g.,Fisher, Laboratory Techniques In Biochemistry And Molecular Biology,eds., Work and Burdon, Elsevier, 1980).

Polypeptides of the invention, particularly short DAF polypeptidefragments, may also be produced by chemical synthesis (e.g., by themethods described in Solid Phase Peptide Synthesis, 2nd ed., 1984 ThePierce Chemical Co., Rockford, Ill.).

These general techniques of polypeptide expression and purification mayalso be used to produce and isolate useful DAF fragments or analogs(described herein).

Anti-DAF Antibodies

Using any of the DAF polypeptides described herein or isolated asdescribed above, anti-DAF antibodies may be produced by any standardtechnique. In one particular example, a DAF cDNA or cDNA fragmentencoding a conserved DAF domain is fused to GST, and the fusion proteinproduced in E. coli by standard techniques. The fusion protein is thenpurified on a glutathione column, also by standard techniques, and isused to immunize rabbits. The antisera obtained is then itself purifiedon a GST-DAF affinity column, for example, by the method of Finney andRuvkun (Cell 63:895–905, 1990), and is shown to specifically identifyGST-DAF, for example, by Western blotting.

Polypeptides for antibody production may be produced by recombinant orpeptide synthetic techniques (see, e.g., Solid Phase Peptide Synthesis,supra; Ausubel et al., supra).

For polyclonal antisera, the peptides may, if desired, be coupled to acarrier protein, such as KLH as described in Ausubel et al, supra. TheKLH-peptide is mixed with Freund's adjuvant and injected into guineapigs, rats, or preferably rabbits. Antibodies may be purified by anymethod of peptide antigen affinity chromatography.

Alternatively, monoclonal antibodies may be prepared using a DAFpolypeptide (or immunogenic fragment or analog) and standard hybridomatechnology (see, e.g., Kohler et al., Nature 256:495, 1975; Kohler etal., Eur. J. Immunol. 6:511, 976; Kohler et al., Eur. J. Immunol. 6:292,1976; Hammerling et al., In Monoclonal Antibodies and T Cell Hybridomas,Elsevier, N.Y., 1981; Ausubel et al., supra).

Once produced, polyclonal or monoclonal antibodies are tested forspecific DAF recognition by Western blot or immunoprecipitation analysis(by the methods described in Ausubel et al., supra). Antibodies whichspecifically recognize a DAF polypeptide described herein are consideredto be useful in the invention. Anti-DAF antibodies, as isolated above,may be used, e.g., in an immunoassay to measure or monitor the level ofDAF polypeptide produced by a mammal or to screen for compounds whichmodulate DAF polypeptide production (for example, in the screensdescribed herein). In one particular example, antibodies to human DAF-7polypeptide are useful for screening blood samples from patients todetermine whether they possess decreased DAF-7 polypeptide levels. Suchantibodies may be used in any immunological assay, for example, an ELISAassay, and a decrease in DAF-7 is taken as an indication of a diabeticcondition, for example, obesity onset Type II diabetes. In anotherparticular example, anti-DAF antibodies are useful for carrying outpedigree analysis. For example, blood samples from individuals may bescreened with anti-DAF-7 antibodies to detect those members of a familywith a predisposition to a diabetic condition. Anti-DAF antibodies mayalso be used to identify cells that express a DAF gene.

DAF-7 Therapy for Obesity-Onset Type II Diabetes

Our data indicates that DAF-7 represents an endocrine hormone formetabolic control that acts synergistically with insulin. Declines inDAF-7 may be induced by obesity, just as the dauer pheromone, a fattyacid, causes declines in C. elegans DAF-7 production.

Accordingly, obesity onset Type II diabetes, glucose intolerance, andthe associated atherosclerosis may be treated if DAF-7 hormone isinjected intramuscularly or intravenously (FIG. 23).

In addition, antibodies to human DAF-7 should detect declines in DAF-7in pre-diabetic, glucose-intolerant, or obesity induced diabetes. Suchantibodies will detect DAF-7 levels in blood, just as insulin levels aredetected in metabolic disease.

DAF-7 therapeutic potential and dosage can be developed in mouse modelsof obesity onset diabetes, for example, the db and ob mouse.

DAF-7 may be injected either intravenously or intramuscularly, inanalogy to insulin therapy.

The decision of which classes of diabetics to treat with DAF-7 will comefrom a combination of blood tests for DAF-7 levels and genetic testingto determine which daf, age, or akt mutations a particular diabetic orpre-diabetic patient carries.

Screening Systems for Identifying Therapeutics

Based on our experimental results, we have developed a number ofscreening procedures for identifying therapeutic compounds (e.g.,anti-diabetic and anti-obesity pharmaceuticals or both) which can beused in human patients. In particular examples, compounds that downregulate daf-3 or daf-16 or their human homologs are considered usefulin the invention. Similarly, compounds that up regulate or activatedaf-1, daf-2, daf-4, daf-7, daf-8, daf-1 daf-14, age-1, or akt (or eachof their corresponding human homologs) are also considered useful asdrugs for the treatment of impaired glucose tolerance conditions, suchas diabetes and obesity. In general, the screening methods of theinvention involve screening any number of compounds for therapeuticallyactive agents by employing any number of in vitro or in vivoexperimental systems. Exemplary methods useful for the identification ofsuch compounds are detailed below.

The methods of the invention simplify the evaluation, identification,and development of active agents for the treatment and prevention ofimpaired glucose tolerance conditions, such as diabetes and obesity. Ingeneral, the screening methods provide a facile means for selectingnatural product extracts or compounds of interest from a largepopulation which are further evaluated and condensed to a few active andselective materials. Constituents of this pool are then purified andevaluated in the methods of the invention to determine theiranti-diabetic or anti-obesity activities or both.

Below we describe screening methods for evaluating the efficacy of acompound as anti-diabetic or anti-obesity agents or both. These examplesare intended to illustrate, not limit, the scope of the claimedinvention.

Test Extracts and Compounds

In general, novel drugs for the treatment of impaired glucose toleranceconditions are identified from large libraries of both natural productor synthetic (or semi-synthetic) extracts or chemical librariesaccording to methods known in the art. Those skilled in the field ofdrug discovery and development will understand that the precise sourceof test extracts or compounds is not critical to the screeningprocedure(s) of the invention. Accordingly, virtually any number ofchemical extracts or compounds can be screened using the exemplarymethods described herein. Examples of such extracts or compoundsinclude, but are not limited to, plant-, fungal-, prokaryotic- oranimal-based extracts, fermentation broths, and synthetic compounds, aswell as modification of existing compounds. Numerous methods are alsoavailable for generating random or directed synthesis (e.g.,semi-synthesis or total synthesis) of any number of chemical compounds,including, but not limited to, saccharide-, lipid-, peptide-, andnucleic acid-based compounds. Synthetic compound libraries arecommercially available from Brandon Associates (Merrimack, N.H.) andAldrich Chemical (Milwaukee, Wis.). Alternatively, libraries of naturalcompounds in the form of bacterial, fungal, plant, and animal extractsare commercially available from a number of sources, including Biotics(Sussex, UK), Xenova (Slough, UK), Harbor Branch Oceangraphics Institute(Ft. Pierce, Fla.), and PharmaMar, U.S.A. (Cambridge, Mass.). Inaddition, natural and synthetically produced libraries are produced, ifdesired, according to methods known in the art, e.g., by standardextraction and fractionation methods. Furthermore, if desired, anylibrary or compound is readily modified using standard chemical,physical, or biochemical methods.

In addition, those skilled in the art of drug discovery and developmentreadily understand that methods for dereplication (e.g., taxonomicdereplication, biological dereplication, and chemical dereplication, orany combination thereof) or the elimination of replicates or repeats ofmaterials already known for their anti-diabetic and anti-obesityactivities should be employed whenever possible.

When a crude extract is found to have anti-diabetic or anti-obesityactivities or both, further fractionation of the positive lead extractis necessary to isolate chemical constituents responsible for theobserved effect. Thus, the goal of the extraction, fractionation, andpurification process is the careful characterization and identificationof a chemical entity within the crude extract having anti-diabetic oranti-obesity activities. The same in vivo and in vitro assays describedherein for the detection of activities in mixtures of compounds can beused to purify the active component and to test derivatives thereof.Methods of fractionation and purification of such heterogenous extractsare known in the art. If desired, compounds shown to be useful agentsfor the treatment of pathogenicity are chemically modified according tomethods known in the art. Compounds identified as being of therapeuticvalue are subsequently analyzed using any standard animal model ofdiabetes or obesity known in the art.

There now follow examples of high-throughput systems useful forevaluating the efficacy of a molecule or compound in treating (orpreventing) an impaired glucose tolerance condition.

Nematode Release of Dauer Arrest Bioassays

To enable mass screening of large quantities of natural products,extracts, or test compounds in an efficient and systematic fashion, C.elegans mutant dauer larvae (e.g., C. elegans containing mutationsdescribed herein, such as C. elegans daf-2 mutant dauer larvae) arecultured in wells of a microtiter plate, facilitating the semiautomationof manipulations and full automation of data collection. In oneparticular example, the assay for dauer release involves a measurementof culture turbidity. Specifically, dauer larvae are treated withcandidate compounds and allowed to incubate. If dauer release occurs,the animals grow and reproduce, and consume their light-scatteringbacterial food source, decreasing the turbidity of the microtiter wellculture. Thus, dauer release is measured by the extent of the decreasein culture turbidity. This type of assay allows millions of microtitersamples to be simultaneously screened.

As discussed above, compounds that down regulate DAF-3 or DAF-16activities or up regulate DAF-1, DAF-2, DAF-4, DAF-7, DAF-8, DAF-11,DAF-14, AGE-1, or AKT activities are considered useful in the invention.Such compounds are identified by their effect on dauer formation in C.elegans strains carrying mutations in these genes (as described above).

In particular examples, nematodes bearing mutations in the DAF-2polypeptide arrest as dauer larvae, never producing progeny. All of themetabolic and growth arrest phenotypes caused by lack of daf-2 aresuppressed by mutations in daf-16. Mutations in the PI 3-kinase, AGE-1,have the same phenotype as lack of daf-2, and such mutations are alsosuppressed by daf-16 mutations. Biochemical analysis of insulinsignaling in mammals supports the view that AGE-1 transduces signalsfrom the DAF-2 receptor by generating a PIP3 signal. Because daf-16mutations suppress lack of daf-2, or age-1 gene activity, it is believedthat PIP3 down regulates or modifies daf-16 gene activity. Thebiochemical overlap between DAF-2/AGE-1 and insulin receptors/PI3-kinase indicates that the human homolog of the C. elegans daf-16 geneacts in the insulin pathway as well. Thus, the C. elegans insulinsignaling pathway yields the surprising result that the animals can livewithout insulin signaling, provided they are mutant in daf-16. Thisanalysis therefore indicates that a compound that inhibits DAF-16activity would reverse the effects of diabetic lesions, e.g., in theproduction or secretion of insulin or in the reception of insulinsignals by target tissues. Such drugs would be expected to beefficacious in the treatment of insulin deficiencies due to pancreatic βcell destruction in Type I diabetes, as well as some Type II diabetesdue to defects in insulin signaling.

To evaluate the ability of a test compound or an extract to decreasedaf-16 gene activity, mutant daf-2 (e1370); daf-16 (mgDf50) animalscarrying an integrated human DAF-16 gene are incubated in microtiterdishes in the presence of a test compound. This human DAF-16 genesupplies all of the DAF-16 activity in the C. elegans strain and thusallows daf-2-induced dauer arrest unless its activity is decreased bythe candidate test compound. If desired, various concentrations of thetest compound or extract can be inoculated to assess the dosage effect.Control wells are incubated in the absence of a test compound orextract. Plates are then incubated at 25° C. After an appropriate periodof time, e.g., 2 to 5 days, wells are examined for progeny. The presenceof progeny is taken as an indication that the test compound or extractis effective at inhibiting daf-3 or daf-16 activity, and therefore isconsidered useful in the invention. Any compound that inhibits DAF-16gene activity (or activates upstream signaling in the absence ofreceptor function) will allow reproduction. This is shown schematicallyin FIG. 19.

Alternatively, a diabetic condition may arise from defects in the DAF-7TGF-β signaling pathway. Since a decrease in DAF-3 activity bypasses theneed for DAF-7 activity in C. elegans metabolic control, drugs that downregulate DAF-3 activity are useful for ameliorating the metabolicdefects associated with diabetes. To screen for such drugs, daf-7(e1372); daf-3 (mg90) nematodes expressing human DAF-3 are exposed tochemicals as described above. In this strain, human DAF-3 supplies allDAF-3 activity, causing daf-7 induced dauer arrest unless its activityis inhibited (FIG. 20). Compounds capable of inhibiting this activityare considered useful therapeutics in the invention.

Finally, in a less complex screen for drugs that inhibit C. elegansdaf-3 or daf-16, daf-7 or daf-2 mutants are directly screened forcompounds that decrease C. elegans daf-3 or daf-16 gene activity.

In addition, C. elegans worms carrying other daf mutations may beutilized in an assay to obtain additional information on the mode ofaction of the test compound in the insulin or TGF-β signaling pathways.For example, a drug having PIP3 agonist activity would be expected toallow age-1 and daf-2 mutants (but not akt or daf-7 mutants) to notarrest at the dauer stage. Similarly, drugs that inhibit daf-3 areexpected to suppress daf-7 mutants but not daf-2 or age-1 mutants.

Exemplary Dauer Recovery Screen

Using screens such as those described above, muscarinic agonists havebeen shown to specifically promote dauer recovery in pheromone-induceddauers as well as particular classes of dauer constitutive mutants.Strikingly, the muscarinic agonists could not induce recovery of daf-2induced dauers, which have defective insulin-like signaling. Thismuscarinic pathway was also shown to regulate A. caninum recovery fromdauer arrest. In mammals, such muscarinic agonists promote insulinrelease both in vivo and in vitro (Ahren et al., (1986) Diabetologia29:827–836; and Miller (1981) Endocr. Rev. 2:471–494). We suggest thatinsulin-like secretory cells in the nematodes are regulated bycholinergic inputs in a metabolic control pathway that is homologous tothe mammalian autonomic input to pancreatic beta cell activity. Drugsthat activate cholinergic as well as other mammalian insulin releasepathways may prove useful in the control of parasitic nematode lifecycles. These experiments were carried out as follows.

Strains and Growth Conditions

All strains were maintained and handled as described in Brenner (1974)Genetics 77:71–94; and Sulston and Hodgkin (1988) Methods (Cold SpringHarbor Laboratory, Cold Spring Harbor. Animals were grown on standard NGagar plates. In this study, the mutations in C. elegans used were LGI:daf-8(e1393); LGII: daf-22(m130); LGIII: daf-7(e1372), daf-2(e1370),daf-4(m63); and LGIV: daf-1(m40), daf-14(m77), daf-10(e1387); LGX:daf-12(m20). Ancylostoma caninum were maintained as described previously(Hawdon and Schad (1993) Exper. Parasitol. 77:489–491).

Dauer Arrest Assay

Minimal media plates were used for the drug assays: 3.0 g NaCl, 20 gagarose (Sigma-Type II #A6877) and 970 ml of water. The autoclavedsolution was cooled to 50–55° C. before 25 ml of 1M KPO₄ (pH 6.0), 1.0ml 1M CaCl₂, 1.0 ml of 1M MgSO₄, and 1 ml of 5 mg/ml cholesterol wereadded. In some assays, Escherichia coli (DH5α) bacteria arrested withstreptomycin was added to each plate.

Animals were grown at 15° C. for several generations and then wereplaced in a bleach solution to isolate eggs. 100–200 eggs were added toeach 10 ml drug plate with food. In several assays, eggs were placed in5–6 ml of S medium (Wood (1988) (Cold Spring Harbor Laboratory Press,Cold Spring Harbor, N.Y.)) in a 15 ml polypropylene tube on a rotaryplatform at 25° C. overnight for 12–16 hours without food. This yields asynchronous preparation of L1 animals. The synchronized L1s were placedonto the drug plates at 20° C. Two, four, and eight days later, plateswere examined for the presence of arrested dauers and reproductivenon-dauers. When the non-dauers had reached the gravid adulthermaphrodite stage and were beginning to lay eggs, each plate wasexamined visually for the presence of dauers and non-dauers. Followingthis, animals from each plate were rinsed off the plate into a plasticdish containing 1% SDS (dauers are the only larval stage resistant tothis treatment). After 30 minutes, dishes were examined under thedissecting microscope for the presence of dauers and non-dauers.

Dauer Recovery Assay

We found that the most effective assay for dauer recovery was to placedauer stage animals onto drug plates at 25° C. without the addition offood. In some experiments, 100–200 eggs or synchronized L1s were putonto the drug plates. For all experiments described herein, about 10,000L1s were placed in 10 ml of S Medium containing 1–2 ml of a 0.4% (w/v)solution of Escherichia coli DH5α bacteria in M9 solution (Wood (1988)(Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y.))arrested with streptomycin, in a 25 ml flask on a rotating heated waterbath at 25° C. For wild-type N2 dauers, 600 μl of the 0.4% bacterialsolution and pheromone was also added to flask as described in Gottlieband Ruvkun (1994) Genetics 137:107120. The pheromone preparation is asolution prepared as follows. Animals were grown in a large flask forseveral generations, and then spun down. The supernatant was boiled downto a brownish powder and then ethanol extracted. After 72 hours ofliquid growth, animals were centrifuged and the supernatant removed.Animals were then resuspended in a 15 ml tube with a pre-heated 25° C.solution of 1% SDS and tubes were placed on a rocker at 25° C. for 30minutes. Animals were centrifuged and the SDS removed. Animals werewashed with either M9 or S medium (Wood (1988) (Cold Spring HarborLaboratory Press, Cold Spring Harbor, N.Y.)) 4–6 times. After a finalspin, 100–200 dauers were placed onto the drug plates without food. 24and 48 hours later, plates were scored for the number of dauers andnon-dauer adults.

For each strain tested, a control plate without any drug, with andwithout food was also tested. With no drug, there was 40% recovery in N2dauers. The high value for the control plate in N2 may have been due toexperimental procedure. The background recovery rate for N2 was muchhigher than the background recovery rate for the dauer constitutivemutants where there was very little, if any, background recovery. Theassay was performed at 25° C., which means that the daf-c mutants arestill under full dauer inducing conditions. However, for N2, noexogenous pheromone was added to the drug plate and therefore, eventhough the plates were kept at a high temperature and had no food,dauer-maintaining conditions may not have been as severe as for thedaf-c mutants.

Drug Assay in A. caninum

Hookworm infective L3 animals were collected from 1–4 wk oldcoproculture by the Baermann technique, and decontaminated with 1% HCLin BU buffer (50 mM Na2PO4/22 mM KH2PO4/70 mM NaCl, pH 6.8) (Hawdon andSchad (1991) in Developmental Adaptations in Nematodes., ed. C. A. Toft,A. A. a. L. B. (Oxford University Press, Oxford), pp. 274–298; andHawdon and Schad (1991) J. Helm. Soc. Wash. 58:140–142) for 30 minutesat 22° C. Approximately 250 L3 animals were incubated in individualwells of a 96-well tissue culture plate containing 0.1 ml RPMI1640tissue culture medium, supplemented with 0.25 mM HEPES pH 7.2, 100 U/mlpenicillin, 100 μg/ml streptomycin, 100 μg/ml gentamycin, and 2.5 μg/mlamphotericin B. The L3 animals were activated to resume development andfeeding by including 10% (v/v) canine serum and 25 mMS-methyl-glutathione (GSM; Hawdon et al. (1995) Exper. Parasitol.80:205–211). Non-activated L3 animals were incubated in RPMI alone(i.e., without the stimulus). Stock solutions of the drugs were made inPMI, and included in the incubation at the indicated concentrations. Thegonists were tested for activation by incubation with the L3 animals inthe absence of the normal stimulus (i.e., serum+GSM), whereas atropinewas tested in the presence of the normal stimulus, as well as with theagonists. The L3 animals were incubated at 37° C. 5% C0₂ for 24 hours.The percentage of feeding L3 animals was determined by incubating the L3animals with 2.5 mg/ml FITC-BSA for 2–3 hours, followed by counting thenumber of L3 animals that had ingested the labeled BSA by microscopicexamination under epi-fluorescent illumination (Hawdon and Schad (1990)J. Parasit. 76:394–398). Each treatment was done in triplicate, and eachexperiment was repeated at least once.

Neurotransmitter Regulation of Diapause

Dauer arrest is modulated by sensory inputs (Golden and Riddle (1984)Developmental Biology 102:368–378). Arrest at the dauer stage iscontrolled by parallel TGF-β and insulin-like signaling pathways (Riddle(1988) in The Nematode Caenorhabditis elegans, ed. Wood, W. B. (ColdSpring Harbor Laboratory Press, Cold Spring Harbor, N.Y.), pp. 393–412;Riddle and Albert (1997) in C. elegans II, eds. Riddle, D. L.,Blumenthal, T., Meyer, B. J. & Priess, J. R. (Cold Spring HarborLaboratory Press), pp. 739–768; Thomas (1993) Bioessays 15:791–797;Riddle et al. (1981) Nature 290:668–671; Vowels and Thomas (1992)Genetics 130:105–123; Thomas et al. (1993) Genetics 134:1105–1117;Gottlieb and Ruvkun (1994) Genetics 137:107120; Georgi et al. (1990)Cell 61:635–645; Estevez et al. (1993) Nature 365:644–649; Ren et al.(1996) Science 274:1389–1391; Kimura et al. (1997) Science 277:942–946;and Morris et al. (1996) Nature 382:536–539.41). Animals arrest at thedauer stage when they are lacking signaling from either of these twopathways (Georgi et al. (1990) Cell 61:635–645; Estevez et al. (1993)Nature 365:644–649; Ren et al. (1996) Science 274:1389–1391; Kimura etal. (1997) Science 277:942–946; and Morris et al. (1996) Nature382:536–539.41). Animals will arrest development at the dauer stage whenhigh levels of pheromone result in the absence of both the DAF-7/TGF-βligand which is secreted from the ASI sensory neuron as well as an asyet unidentified secretory cell that releases the insulin-like ligand.Lack of the TGF-β ligand results in an upregulation of the DAF-3 Smadprotein, while lack of the insulin-like ligand causes an upregulation ofthe DAF-16 forkhead transcription factor. Therefore, for dauer arrest,two separate signaling pathways are involved. Recovery from the dauerarrest when pheromone levels decline is thought to involve up-regulationof these TGF-β and insulin-like signals.

To detect possible neural inputs to this neuroendocrine system, wetested drugs that affect a variety of neurotransmitter signalingpathways, including agonists, antagonists, and reuptake inhibitors, foreffects on either dauer arrest or dauer recovery. We have shown thatmuscarinic agonists (oxotremorine, arecoline, pilocarpine and muscarine)promoted dauer recovery. None of the drugs tested promoted dauer arrestunder replete conditions.

Cholinergic Input to Dauer Recovery

We tested drugs that affected the following mammalian neuronal pathways:adrenergic/noradrenergic, serotonergic, cholinergic, glutaminergic,dopaminergic, gabaergic and opiod for effects on C. elegans dauerinduction and dauer recovery. In each category both agonists andantagonists were examined. Most drugs tested did not affect dauerrecovery and the animals remained arrested at the dauer stage. However,multiple unrelated muscarinic agonists could promote dauer recovery.Four muscarinic agonists, oxotremorine, pilocarpine, arecoline, andcarbachol (Avery et al. (1993) Genetics 134:455–464), promoted recoveryof dauers induced by mutation as well as pheromone. The dose responsecurves in FIGS. 44A–44C show the muscarinic agonists induced about 50%recovery of dauers induced by defective TGF-β signaling in thedaf-7(e1372) mutant, with a defect in the TGF-β ligand. Similar resultswere seen with other mutants in the TGF-β signaling pathway, daf-1(m40)in the type I TGF-β receptor and daf-4(m63) in the type II TGF-βreceptor. For example, 30% of daf-1(m40) dauers recover in oxotremorine,whereas plates with no drug had less than 5% recovery. Similarly, 50% ofdaf-4(m63) dauers recover in oxotremorine, while plates with no drug hadless than 1% recovery.

The infective “dauer” L3 of the hookworm A. caninum can be stimulated toresume feeding and development in vitro by incubation with canine serumand S-methyl-glutathione (GSM), but not by tissue culture medium alone(Sulston and Hodgkin (1988) Methods (Cold Spring Harbor Laboratory, ColdSpring Harbor)). However, when A. caninum L3 were incubated with eitheroxotremorine or arecoline in the tissue culture medium, 60–80% of theanimals recovered, as indicated by the resumption of feeding. Therefore,muscarinic agonists mimicked the recovery induced by serum and GSM.

FIGS. 44A–44C show the dose response curves of two of the muscarinicagonists tested: oxotremorine and arecoline. In each figure we show thedose response for wild-type induced dauers, daf-7(e1372), daf-2(e1370)and A. caninum dauers. Pilocarpine (data not shown) and oxotremorine(FIG. 44A) induced maximum recovery of daf-7(e1372) dauers at 5 mMconcentration, while wild-type pheromone-induced dauers reached maximumrecovery at 1 mM. A. caninum L3 dauers also reached maximum recovery at5 mM oxotremorine (FIG. 44A), but failed to recover when incubated withpilocarpine. The maximal response for arecoline was 10 fold lower thanfor the other agonists in both C. elegans and A. caninum (FIG. 44B).Concentrations of 1 mM to 5 mM of a drug are routinely used in drugassays in C. elegans (Hart et al. (1995) Nature 378:82–85.21; Horvitz etal. (1982) Science 216:1012–1014; Lewis et al. (1980) Genetics95:905–928; Lewis et al. (1980) Neuroscience 5:967–989; Maricq et al.(1995) Nature 378:78–81; McIntire et al. (1993) Nature 364:334–337;McIntire et al. (1993) Nature 364:337–341; Schinkmann and Li (1992) J.Comp. Neurol. 316:251–260.51; and Avery et al. (1993) Genetics134:455–464). The unusually high doses may be due to a cuticlepermeability barrier.

While the muscarinic agonists were potent inducers of recovery in daf-7induced and pheromone-induced dauers, they did not induce recovery of adaf-2 mutant with defects in the C. elegans homologue of the mammalianinsulin receptor gene (FIG. 44A-44C). Thus the muscarinic recoverypathway depends on insulin-like signaling. Atropine specificallyinhibits dauer recovery

To determine the specificity of the muscarinic response, we added bothoxotremorine, the agonist, and atropine, a muscarinic antagonist, toplates varying the concentration of antagonist to obtain a dose responseshown in FIG. 44C. In 1 mM oxotremorine, 40% of the daf-7(e1372) dauersrecovered. However, in combination with 1 mM atropine, 1 mM oxotremorineonly induced 5% recovery; at 5 mM atropine, the 1 mM oxotremorineresponse was completely abolished. For wild-type N2 dauers, the resultswere almost identical (FIG. 44C). This suggested that the drug-inducedrecovery was a specific muscarinic response, since in mammals atropineis only a muscarinic antagonist and did not interfere with nicotinicreceptors (Lefkowitz et al. (1996) in Goodman and Gilman's ThePharmacological Basis of Therapeutics, eds. Hardman, J. G. & Limbird, L.E., McGraw Hill, pp. 105–139; and Brown and Taylor (1996) in Goodman andGilman's The Pharmacological Basis of Therapeutics, eds. Hardman, J. G.& Limbrid, L. E., McGraw Hill, pp. 141–160).

Atropine (0.5 mM) inhibited recovery of A. caninum L3 incubated withserum and GSM by 99.5%. Moreover, A. caninum L3 incubated with 0.5 mMarecoline and 1.0 mM atropine failed to recover (FIG. 44C). These dataindicate that recovery from arrest in hookworm L3 is also mediated by amuscarinic signal.

Atropine inhibits C. elegans dauer recovery induced by food signals.When killed bacteria are added to pheromone-induced dauers at 25° C.,99% of the animals recovered (FIG. 45A). Without bacteria, no dauersrecovered in the same time period (FIG. 45A). However, only 21% of thedauer larvae recovered in bacterial food plus atropine (FIG. 45A).Similarly, atropine (0.5 mM) inhibited recovery of A. caninum L3incubated with serum and GSM by 99.5%.

Temperature is a potent inducer of dauer recovery in animals bearingmutations in the TGF-β or insulin-like signaling pathways. For example,null mutations in daf-7 are temperature sensitive, and recovery of bothdaf-7 and daf-2-induced dauer larvae was stimulated by shift to 15° C.(FIG. 45A). Temperature downshift in the absence of food did not inducedauer recovery in either daf-7 or daf-2 mutants (FIG. 45A) nor didbacterial food at 25° C. allow non dauer development. However,temperature downshift and addition of food induced more than 75%recovery of both mutants. This recovery in both daf-7 and daf-2 mutantswas inhibited by atropine (FIG. 45A-45B).

We tested whether it was necessary to have functioning sensory neuronsto mediate the muscarinic induced response. daf-10 mutants have abnormalmechanocilia and irregular contours in the amphid sensilla. Adaf-7(e1372); daf-10(e1387) double mutant gave a maximum response of 13%recovery with 1 mM oxotremorine. This suggests that the amphid neuronsare necessary to meditate the muscarinic response. Alternatively, it ispossible that the amphid defects do not allow the drug to enter theworm, if the drug indeed does penetrate the worm through these neurons.

We also examined whether exogenous application of neurotransmitterscould mimic the dauer pheromone to induce dauer arrest. We tested thesedrugs for induction of dauer arrest in wild-type and daf-22 mutants.daf-22 is a mutant that does not secrete pheromone, but will arrest atthe dauer stage when exposed to exogenous pheromone (Golden and Riddle(1985) Molecular and General Genetics 198:534–536). None of the drugstested caused dauer entry under favorable growth conditions. The drugswere active in the plate because several of the drugs caused eitherparalysis, death, or egg-laying defects.

Dauer Recovery by Muscarinic Agonists

Arrest at the dauer stage is a nematode survival strategy that is aspecific example of the related and phyletically general diapausearrest. In C. elegans, dauer arrest occurs under harsh environmentalconditions whereas in the hookworm, A. caninum, a parasitic nematode,diapause is a non-conditional stage in the life cycle (Riddle and Bird(1985) J. Nematol. 17:165–168; and Schmidt and Roberts (1985)Foundations of Parasitology (Times Mirros/Mosby College Publishing)).Dauer recovery is regulated by levels of pheromone, food, andtemperature in C. elegans, whereas in A. caninum unknown host factorsinduce dauer recovery upon infection (Golden and Riddle (1984)Developmental Biology 102:368–378).

We have shown that muscarinic agonists cause dauer recovery in both C.elegans and A. caninum, and that this recovery is specifically inhibitedby the muscarinic antagonist atropine. The endogenous neurotransmitterat muscarinic receptors is acetylcholine, which in vertebrates functionsat cholinergic synapses in both the peripheral and central nervoussystem (Brown and Taylor (1996) in Goodman and Gilman's ThePharmacological Basis of Therapeutics, eds. Hardman, J. G. & Limbird, L.E., McGraw Hill, pp. 141–160). Acetylcholine has a wide variety offunctions in vertebrate signaling including sympathetic andparasympathetic ganglion cells as well as the adrenal medulla, synapseswithin the central nervous system, and motor end plates on skeletalmuscle innervated by somatic motoneurons (Brown and Taylor (1996) inGoodman and Gilman's The Pharmacological Basis of Therapeutics, eds.Hardman, J. G. & Limbird, L. E., McGraw Hill, pp. 141–160). Muscarinicreceptors are found in muscle, the autonomic ganglia, the centralnervous system and secretory glands. These receptors couple to Gproteins and signal on longer time scales than nicotinic receptors.Signaling can be either excitatory or inhibitory (Lefkowitz et al.(1996) in Goodman and Gilman's The Pharmacological Basis ofTherapeutics, eds. Hardman, J. G. & Limbird, L. E., McGraw Hill, pp.105–139). Both muscarinic and nicotinic receptors have been found ininvertebrates such as Drosophila and C. elegans as well as vertebrates(Lewis et al. (1980) Genetics 95:905–928; Dudai and Ben-Barak (1977)FEBS Lett. 81:134–136; Haim et al. (1979) J. Neurochem. 32:543–522; andCulotti and Klein (1983) J. Neurosci. 3:359–368).

The nicotinic receptor has been the primary focus of the studies oncholinergic signaling in the worm. The drug levamisole, a nicotinicagonist, is toxic to animals, causing muscle hypercontraction (Lewis etal. (1980) Genetics 95:905–928; and Lewis et al. (1980) Neuroscience5:967–989). Mutants that are resistant to this drug have revealedcomponents of a nicotinic signaling cascade (Lewis et al. (1980)Genetics 95:905–928; and Lewis et al. (1980) Neuroscience 5:967–989).Levamisole has no effect on dauer recovery, suggesting that thenicotinic receptor pathway does not regulate dauer arrest.

Fewer studies, however, have been done on muscarinic signaling in C.elegans. Binding studies on crude homogenates of C. elegans have shownthat they contain muscarinic receptors that have the potential to bindto the muscarinic ligands, [3H] QNB (Yamamura & Snyder (1974) Proc.Natl. Acad. Sci. ?:1725–1729) and [3H] N-methylscopalamine(Burgermeister et al. (1978) Mol. Pharmacol. 14:240–256) with highaffinity (Culotti and Klein (1983) J. Neurosci. 3:359–368). Thesereceptors were found in both C. elegans adults and L1 and L2 larvae((Culotti and Klein (1983) J. Neurosci. 3:359–368). Several potentialmuscarinic receptor homologues have been identified in the C. elegansgenome sequence database (Sulston et al. (1992) Nature 356:37–41)

There are two different classes of muscarinic receptor agonists: cholineesters and cholinomimetic allkaloids. Both arecoline and pilocarpine arenaturally occurring drugs from the betel nut seed and the Pilocarpusleaf, respectively, while oxotremorine is a synthetic drug (Brown andTaylor (1996) in Goodman and Gilman's The Pharmacological Basis ofTherapeutics, eds. Hardman, J. G. & Limbird, L. E., McGraw Hill, pp.141–160). Carbachol is a synthetic choline ester which mimicsacetylcholine and acts at both muscarinic and nicotinic receptors inmammals (Brown and Taylor (1996) in Goodman and Gilman's ThePharmacological Basis of Therapeutics, eds. Hardman, J. G. & Limbird, L.E., McGraw Hill, pp. 141–160). Arecoline, pilocarpine, and oxotremorineare drugs that have the same sites of action and function as the cholineesters (Brown and Taylor (1996) in Goodman and Gilman's ThePharmacological Basis of Therapeutics, eds. Hardman, J. G. & Limbird, L.E., McGraw Hill, pp. 141–160). Arecoline also acts on nicotinicreceptors. Atropine specifically inhibits mammalian muscarinic responses(Brown and Taylor (1996) in Goodman and Gilman's The PharmacologicalBasis of Therapeutics, eds. Hardman, J. G. & Limbird, L. E., McGrawHill, pp. 141–160). Since all of the drug-induced dauer recovery wasinhibited by atropine, we concluded that this response was mediated bymuscarinic signaling.

Molecular analysis of the dauer mutants revealed that a TGF-β signalingpathway regulated dauer arrest (FIG. 46). Mutations in daf-7, whichencodes a TGF-β ligand, caused animals to arrest at the dauer stage evenunder favorable growth conditions (Ren et al. (1996) Science274:1389–1391). The same phenotype was observed in animals bearing amutation in either of the two TGF-β receptors, daf-1 and daf-4 (Georgiet al. (1990) Cell 61:635–645; and Estevez et al. (1993) Nature365:644–649; FIG. 46). Downstream of the receptors are members of theSmad signaling group including the genes daf-8, daf-14 and daf-3 (FIG.46). Muscarinic agonists potently induced recovery of dauer larvaeinduced by mutations in this group of genes (FIG. 44A-44C).

An insulin-like signaling pathway represented by daf-2 and age-1functions in parallel to this TGF-β pathway (Riddle et al. (1981) Nature290:668–671; Vowels and Thomas (1992) Genetics 130:105–123; Thomas etal. (1993) Genetics 134:1105–1117; Gottlieb and Ruvkun (1994) Genetics137:107120; Kimura et al. (1997) Science 277:942–946; and Morris et al.(1996) Nature 382:536–539.41; FIG. 46). daf-2 is a member of the insulinreceptor family (Kimura et al. (1997) Science 277:942–946) and age-1encodes phosphatidylinositol (PI)-3-kinase (Morris et al. (1996) Nature382:536–539.41) suggesting that the level of an insulin-like molecule isdown-regulated during pheromone-induced dauer arrest. None of the drugstested, including the muscarinic agonists and antagonists, could inducedauer recovery in daf-2 mutants (FIG. 44A-44C). Thus the cholinergicinput to dauer recovery depends on insulin-like signaling. We suggestthat muscarinic agonists induce recovery of the TGF-β pathway mutantdauer larvae or pheromone-induced dauer larvae by stimulating signalingin the daf-2 insulin-like pathway. In this way, cholinergic stimulationcan induce recovery in animals with defective TGF-β pathway genes butnot in animals with defect insulin-like pathway genes.

In vertebrate insulin signaling, many studies link muscarinic andinsulin signaling pathways. Both adrenergic and cholinergic fibersinnervate secretory cells in the vertebrate islet of Langerhans (Ahrenet al. (1986) Diabetologia 29:827–836; and Yamamura and Snyder (1974)Proc. Natl. Acad. Sci. 1725–1729). Consistent with the suggestion thatmuscarinic inputs increase C. elegans insulin-like signaling, mammalianautonomic cholinergic fibers enhance insulin secretion. Pharmacologicalstimulation with acetylcholine or carbachol can induce insulin releaseboth in vivo and in vitro. This induction is completely abolished byatropine, showing that it is mediated by activation of muscarinicreceptors on the β cells (Ahren et al. (1986) Diabetologia 29:827–836;Boschero et al. (1995) Am. J. Physiol. 268:E336–E342; and Latifpour etal. (1992) J. Urol. 147:760–763). In mammalian systems, binding ofacetylcholine to the β cell muscarinic receptor causes activation ofsodium channels, which in turn leads to a change in membrane potentialto induce insulin.

These data suggest the model shown in FIG. 46 for dauer recovery in C.elegans. When pheromone levels decrease and food levels increase,acetylcholine is secreted from an as yet unidentified neuron and bindsto the muscarinic receptor on an insulin-like secreting neuron or othercell. This induces secretion of an insulin-like signal to in turn inducedauer recovery (FIG. 46). The lack of muscarinic induced dauer recoveryin daf-2 mutants suggest that the insulin-like dauer recovery signalacts via the DAF-2 receptor homologue. From analogy with the vertebratestudies, we suggest that a muscarinic signal causes an increase ininsulin release that would bind to the DAF-2 receptor and activatedownstream genes which promote dauer recovery. We suggest that theinsulin-like DAF-2 ligand is produced by neurons just as the DAF-7 TGF-βsignal is produced by the ASI sensory/secretory neuron. Insulinsecreting pancreatic β-cells have many neuronal features and are thoughtto be specialized “ganglia” related to the enteric nervous system oflower vertebrates. In addition, proteins related to insulin are producedby metabolism regulating neurons in Limulus. Distant relatives ofinsulin are found in the C. elegans genome database. We suggest that thesecretory cells that express such an insulin-like gene will also expressmuscarinic receptors and be connected to food, pheromone, andtemperature sensory neurons.

Temperature acts as a modulator for dauer recovery (Riddle and Albert(1997) in C. elegans II, eds. Riddle, D. L., Blumenthal, T., Meyer, B.J. & Priess, J. R., Cold Spring Harbor Laboratory Press, pp. 739–768,FIG. 45A-B). The thermoregulatory circuit for temperature sensation andoutput of that information to motor and endocrine pathways has beenidentified (Hobert et al. (1997) Neuron 19:345–357). This pathwayconsists of the thermosensory neuron AFD coupled to the intemeurons AIYand AIZ (Hobert et al. (1997) Neuron 19:345–357; and Henquin (1994) inJoslin's Diabetes Mellitus, eds. Kahn, C. R. & Weir, G. C., (Lea &Febiger, pp. 56–80)). Mutations in the gene ttx-3, which affect AIYfunction and is expressed exclusively in the AIY interneurons (Hobert etal. (1997) Neuron 19:345–357), decouple this thermoregulatory pathwayfrom the dauer pathway: daf-7; ttx-3 double mutant animals form dauersthat recover at high temperature, unlike daf-7 single mutants (Hobert etal. (1997) Neuron 19:345–357). However, daf-2;ttx-3 double mutant dauersdo not recover at high temperature, like the daf-2 mutant alone. Wesuggest that thermosensory signals through the thermoregulatory AIY andAIZ intemeurons couple via as yet unidentified insulin-like secretoryneurons (FIG. 46). Given that rates of growth and metabolism areintimately connected to cultivation temperature in invertebrates, thecoupling of thermosensation to metabolic control is reasonable. Such acoupling of thermosensory input to metabolic control by the daf-2insulin-like signaling pathway is analogous to the hypothalamicmodulation of autonomic input to the pancreatic beta cells.

The muscarinic signaling pathway also acts in recovery of hookworminfective L3 from their arrested “dauer” state. Recovery from dauerarrest in hookworm occurs in the definitive host in response to anundefined host-specific signal. We suggest that upregulation of aninsulin-like molecule by a cholinergic pathway also causes dauerrecovery upon entry into the host in A. caninum. Accordingly, suchparasite insulin-like signals provide targets for anti-helminthic drugs.For example, known muscarinic signaling drugs may constitute novelchemotherapeutic strategies to perturb the dauer maintainence process ininvertebrate hosts as well as the recovery process in human hosts.

Other Screening Assays

Other drug screening assays may also be performed using either C.elegans worms or mammalian cell cultures. If desired, such assays mayinclude the use of reporter gene constructs.

For example, evaluation of the effects of test compounds on dauerformation or reporter gene expression in mutant C. elegans strainsexpressing particular human homologs of the daf age, or akt genes (i.e.,humanized C. elegans) represent useful screening methods. Expression ofthe human homologs in C. elegans is accomplished according to standardmethods and, if desired, such genes may be operatively linked to a genepromoter obtained from C. elegans. Such promoters include, withoutlimitation, the C. elegans daf-16, age-1, daf-3, daf-4, and akt genepromoters. For example, the 2.5 kb age-1 promoter can be generated andisolated by employing standard PCR methods using the following primers:5′GGAAATATTTTAGGCCAGATGCG3′ (SEQ IS NO: 49) and 5′CGGACAGTCCTGAATACACC3′(SEQ ID NO: 50).

Additionally, mammalian tissue culture cells expressing C. elegans daf;age-1, or akt homologs may be used to evaluate the ability of a testcompound or extract to modulate the insulin or TGF-β signaling pathways.Because the signaling pathways from the ligands, receptors, kinasecascades, and downstream transcription factors are conserved from man toworm, test compounds or extracts that inhibit or activate the wormsignaling proteins should also inhibit or activate their respectivehuman homolog. For example, our identification that DAF-16 is atranscription factor that acts downstream of insulin-like signaling inC. elegans indicates that human DAF-16 transcription reporter genes alsocan be used to identify drugs that inhibit any of the kinases in thesignaling pathway downstream of insulin signaling. For example, the useof DAF-16 and DAF-3 protein binding sites in reporter gene constructsmay be used to monitor insulin signaling. Candidate compounds mimickinginsulin signaling (e.g., PIP3 agonists) are expected to increasereporter gene expression and are considered useful in the invention.

Reporter Gene Construct

In one particular example, the invention involves the use of a reportergene that is expressed under the control of a C. elegans gene promoter,e.g., a promoter that includes the TCTCGTTGTTTGCCGTCGGATGTCTGCC (SEQ IDNO: 51) enhancer element, such as the C. elegans pharyngeal myosinpromoter (Okkema and Fire, Development 120: 2175–2186, 1994). Thisenhancer element is known to respond to DAF-3 regulation (i.e., in daf-7mutants, where daf-3 is active, the element confers low level expressionto reporter genes; whereas in a daf-7; daf-3 mutant (for example, daf-7(e1372); daf-3), the element confers low level expression to reportergenes). Other equivalent enhancer elements may also be used in theinvention, e.g., the enhancer element which is bound by the XenopusSmad1 and Fast1 forkhead proteins (Nature 383 600–608, 1996). Theenhancer element is cloned upstream of any standard reporter gene, e.g.,the luciferase or green fluorescent protein (GFP) reporter genes. Inpreferred embodiments, the GFP reporter gene is used in C. elegans. Inother preferred embodiments, either the GFP or the luciferase reportergenes may be used in a mammalian cell based assay. The reporter geneconstruct is subsequently introduced into an appropriate host (e.g., C.elegans or a mammalian cell) according to any standard method known inthe art. Analysis of reporter gene activity in the host organism or cellis determined according to any standard method, e.g., those methodsdescribed herein. Such reporter gene (and host cell systems) are usefulfor screening for drugs that modulate insulin or DAF-7 metabolic controlsignaling.

In addition, any number of other transcriptional fusions to fat basedmetabolic genes, such as fatty acid synthase, hormone sensitive lipaseorthologue, and acetyl coa synthase, may also be constructed. Thesegenes are expected to be Up regulated when the animals shift to fatbased metabolism and to be directly regulated by DAF-16 and DAF-3, andperhaps DAF-12.

Transcriptional fusions to GFP allow the screening of drugs or mutantsfor altered regulation of these genes and altered metabolism. Such drugsor gene targets are useful in the control of obesity and diabetes. Forexample, drugs that inactivate the expression of fat synthesis genes inC. elegans may be used to treat diabetes and obesity. Similarly, fulllength protein fusions of these genes to GFP reveal the subcellularlocalization of the proteins. Drugs or mutants that perturb the cellbiology of these proteins also provide useful treatments and drugtargets for obesity control as well as diabetes.

Shown below are conserved protein regions of C. elegans homologues ofkey metabolic enzymes SEQ ID NOS:211–303). GFP fusions maybe constructedusing the 5′ promoter regions located between these conserved proteindomains and the next gene located 5′ to these regions, as describedabove for the glucose transporter GFP fusion gene.

Pepck >R11A5 Length = 26,671 Plus Strand HSPs: Score = 994 (461.5 bits),Expect = 0.0, Sun P (5) = 0.0 Identities = 176/223 (78%), Positives= 195/223 (87%), Frame = +1 Query: 201AKNNGEFVRCVHSVGQPKPVATKVINHWPCNPEKTIIABRPAEREIWSFGSGYGGNSLLG 260A  N +FVRC+HSVG P+PV  +VINGWPCNPE+ +IAHRP EREIWSFGSGYGGNSLLG Sbjct: 8682ALGNQDFVRCIHSVGLPRPVKQRVINHWPCNPERVLIAHRPPEREIWSFGSGYGGNSLLG 18861Query: 261 KKCFALRIANNIGYDEGWMAEHMLIMGVTSPKGEERFVAAAFPSACGKTNLAMLEPTIPG320 KKCFALRIA NI  DEGWNAEHMLIMGVT P G E F+AAAFPSACGKTNLAMLEPT+PG Sbjct:18862 KKCFALRIASNIAKDEGWMAEHMLIMGVTRPCGREHFIAAAFPSACGKTNLAMLEPTLPG 19041Query: 321 WKVRVIGDDIAWNKFGADGRLYAINPEYGFFGVAPGTSHKTNPNAMASFQENTIFTNVAE380 WKVR +GDDIAWMKFG DGRLYAINPE GFFGVAPGTS+KTNPMA+A+FQ+N+IFTNVAE Sbjct:19042 WKVRCVGDDIAWMKFGEDGRLYAINPEAGFFGVAPGTSNKTNPMAVATFQKNSIFTNVAE 19221Query: 381 TADGEYFWEGLEHEVKNPKVDMINWLGEPWHIGDESKAAHPNS  423TA+GEYFWEGLE E+ +  VD+  WLGE WHIG+   AAHPNS Sbjct: 19222TANGEYFNEGLEDEIADKNVDITTWLGEKWHIGEPGVAAEPNS  19350 Score = 657 (305.1bits), Expect = 0.0, Sun P (5) = 0.0 Identities = 120/173 (69%),Positives = 144/173 (83%), Frame = +1 Query: 32KGDFVSLPKNVQRFVAEKAELMKPSAIFICDGSQNEADELIARCVERGVLVPLKAYKNNY 91+GDF  LP  VQRF+AEKAELM+P  IFICDGSQ+EADELI + +ERG+L  L+AY+NNY Sbjct:18181 QGDFHLLPAKVQRFIAEKAELMRPRGIFICDGSQHEADELIDKLIERGMLSKLEAYENNY 18360Query: 92 LCRTDPRDVARVESKTWMITPEKYDSVCHTPEGVKPMMGQWMSPDEFGKELDDRFPGCMA151 +CRTDP+DVARVESKTWM+T  KYD+V HT EGV+P+MG W++P++   ELD RFPGCMA Sbjct:18361 ICRTDPKDVARVESKTWMVTKNKYDTVTHTKEGVEPIMGHWLAPEDLATELDSRFPGCMA 18540Query: 152 GRTMYVIPYSMGPVGGPLSKIGIELTDSDYVVLCMRIMTRMGEPVLKALAKNN  204GR MYVIP+SMGPVCGPLSKIGI+LTDS+YVVL MRIMTR+   V  AL   + Sbjct: 18541GRIMYVIPFSMGPVGGPLSKIGIQLTDSNYVVLSMRIMTRVNNDVWDALGNQD  18699 Score = 453(210.3 bits), Expect = 0.0, Sum P (5) = 0.0 Identities = 77/107 (71%),Positives = 90/107 (84%), Frame = +1 Query: 424RFTAPAGQCPIIHPDWEKPEGVPIDAIIFGGRRPEGVPLVFESRSWVHGIFVGACVKSEA 483RF APA QCPIIHPDWE P+GVPI+AIIFCCRRP+GVPL++E+ SW HG+F G+C+KSEA Sbjct:19396 RFAAPANQCPIIHPDWESPQGVPIEAIIFGGRRPQCVPLIYETNSWEHGVFTGSCLKSEA 19575Query: 484 TAAAEHTGKQVMHDPMANRPFMGYNFGRYMRHWMKLGQPPHKVPKIF  530TAAAE TGK VMHDPMANRPFMGYNFG+Y++HW+ L     KV+++F Sbict: 19576TAAAEFTGKTVMHDPMAMRPFMGYNFGKYLQHWLDLKTDSRKVIDFF  19716 Score = 404(187.6 bits), Expect = 0.0, Sum P (5) = 0.0 Identities = 68/116 (58%),Positives = 89/116 (76%), Frame = +1 Query: 526VPKIFHVNWFRQSADHKFLWPGYGDNIRVIDWILRRCSGDATIAEETPIGFIPKKGTINL 585+PKI+HVNWFR+ +++KFLWPG+GDNIRVIDWI+RR  G+  I  ETPIG +P KC+INL Sbjct:19760 MPKIYHVNWFRKDSNNKFLWPGFGDNIRVIDWIIRRLDGEQEIGVETPICTVPAKGSINL 19929Query: 586 EGLPNVNWDELMSIPKSYWLEDMVETKTFFENQVGSDLPPEIAKELEAQTERIKAL 641EGL  VNWDELMS+P  YW +D  E + F + QVG DLP  +  E++AQ +R++ L Sbjct: 19930EGLGEVNWDELMSVPADYWKQDAQEIRKFLDEQVGEDLPEPVRAEMDAQEKRVQTL 20097 Score= 69 (32.0 bits), Expect = 0.0, Sum P (5) = 0.0 Identities = 15/36(41%), Positives = 21/36 (58%), Frame = +1 Query: 5SLSHFKDDDFAVVSEVVTHKQNHIPVIKGDFVSLPK 40SL    +D F VV+EVV  +  H+P++K  F S  K Sbjct: 14722SLRQISEDAFYVVNEVVMKRLGHVPILKVIFESSEK 14829 Score = 39 (18.1 bits),Expect = 6.9e−244, Sum P (4) = 6.9e−244 Identities = 9/25 (36%),Positives = 11/25 (44%), Frame = +3 Query: 148 GCMAGRTMYVIPYSMGPVGGPLSKI172 GC   R + V P S      PL K+ Sbjct: 8040 GCSCRRVLCVCPCSHSSSALPLQKV 8114Score = 38 (17.6 bits), Expect = 4.0e−285, Sum P (5) = 4.Oe−285Identities = 7/16 (43%), Positives = 9/16 (56%), Frame = +1 Query: 588LPNVNWDELMSIPKSY 603 L+NW    + S P SY Sbjct: 22654 LESFNWFSFVSCPDSY22701 Score = 37 (17.2 bits), Expect = 2.0e−48, Sum P (3) = 2.0e−48Identities = 6/14 (42%), Positives = 9/14 (64%), Frame = +1 Query: 117SVCHTPEGVKPMMG 130 +V H P  ++P MG Sbjct: 19603 TVNHDPMANRPFMG 19644Acetyl coa carboxylase >W09B6 Length = 32,900 Plus Strand HSPs: Score= 562 (259.1 bits), Expect = 0.0, Sum P (14) = 0.0 Identities 109/197(55%), Positives = 138/197 (70%), Frame = +2 Query: 1951SGFFDYGSFSEIMQPWAQTVVVGRARLGGIPVGVVAVETRTVELSVPADPANLDSEAKII 2010+G  D  SF EI   WA+++V GRARL GIP+GVV+ E R VPADPA       S+ + Sbjct: 28280TGICDTMSFDEICGDWAKSIVAGRARLCGIPIGVVSSEFRNFSTIVPADPAIDGSQVQNT 28459Query: 2011 QQAGQVWFPDSAFKTYQAIKDFNREGLPLMVFANWRGFSGGMKDMYDQVLKFGAYIVDGL2070 Q+AGQVW+PDSAFKT +AI D N+E LPLM+ A+ RGFSGG KD YD VLKFGA IVD L Sbjct:28460 QRAGQVWYPDSAFKTAEAINDLNKENLPLMIIASLRGFSGGQKIMYDMVLKFGAQIVDAL 28639Query: 2071 RECSQPVMVYIPPQAELRGGSWVVIDPTINPRHMEMYADRESRGSVLEPEGTVEIKFRKK2130    ++PV+VYIP   ELRGG+W V+D  I P  + + AD +SRG +LEP   V IKFRK Sbjct:28640 AVYNRPVIVYIPEAGELRGGAWAVLDSKIRPEFIHLVADEKSRQGILEPNAVVGIKFRKP 28819Query: 2131 DLVKTMRRVDPVYIRLA  2147  +++ M+R DP Y +L+ Sbjct: 28820MMMEMMKRSDPTYSKLS  28870 Score = 357 (164.6 bits), Expect = 0.0, Sum P(14) = 0.0 Identities = 68/124 (54%), Positives = 89/124 (71%), Frame= +2 Query: 303VGYPVMIKASEGGGGKGIRKVNNADDFPNLFRQVQAEVPGSPIFVNRLAKQSRHLEVQIL 362+G+P+MIKASEGGGGKGIRK    +DF ++F +V  EV GSPIF+M+    +RH+EVQ+L Sbjct:23264 IGFPLMIKASEGGGGKGIRKCTKVEDFKSMFEEVAQEVQGSPIFLMKCVDGARHIEVQLL 23443Query: 363 ADQYGNAISLFGRDCSVQRRHQKXXXXXXXXXXXXXVFEHMEQCAVKLAKMVGYVSAGTV422 AD+Y N IS++ RDCS+QRR QK             + + M++ AV+LAK VGY SAGTV Sbjct:23444 ADRYENVISVYTRDCSIQRRCQKIIEEAPAIIASSHIRKSMQEDAVRLAKYVGYESAGTV 23623Query: 423 EYLY  426 EYLY Sbjct: 23624 EYLY  23635 Score = 345 (159.1bits), Expect = 0.0, Sum P (14) = 0.0 Identities = 65/116 (56%),Positives = 86/116 (74%), Frame = +2 Query: 1787KEEGLGAENLRGSGMIAGESSLAYDEIITISLVTCRAIGIGAYLVRLGQRTIQVENSHLI 1846K E +G ENL+GSG+IAGE++ AY E+ T   VT R++GIGAY  RL  R +Q + SHLI Sbjct:27794 KNEKIGVENLQGSGLIAGETARAYAEVPTYCYVTGRSVGIGAYTARLAHRIVQHKQSHLI 27973Query: 1847 LTGAGALNKVLGREVYTSNNQLGQIQIMHNNGVTHCTVCDDFEGVFTVLHWLSYMP1902 LTG  ALN +LG++VYTSNNQLGG ++M  NGVTH  V +D EG+  V+ W+S++P Sbjct:27974 LTGYEALNTLLGKKVYTSNNQLGGPEVNFRNGVTHAVVDNDLEGIAKVIRWMSFLP 28141Score = 319 (147.1 bits), Expect = 0.0, Sum P (14) = 0.0 Identities= 59/119 (49%), Positives = 80/119 (67%), Frame = +2 Query: 503HVIAARITSENPOEGFKPSSGTVQELNFRSNKNVWGYFSVAAAGGLHEFADSQFGHCFSW 562H IAARIT ENPD+ F+PS+G V E+NF S+++ W YFSV     +H+FADSQFGH F+ Sbjct: 23870HAIAARITCENPDDSFRPSTGKVYEINFPSSQDAWAYFSVGRGSSVHQFAOSQFGHIFTR 24049Query: 563 GENREEAISNMVVALKELSIRGDFRTTVEYLIKLLETESFQLNRIDTGWLDRLIAEKVQ621 G +R EA++ M   LK ++IR  F T V YL+ L+    F  N  +T WLD+ IA K++ Sbjct:24050 GTSRTEANNTMCSTLKHMTIRSSFPTQVNYLVDLMHDADFINNAFNTQWLDKRIAMKIK 24226Score = 303 (139.7 bits), Expect = 0.0, Sum P (14) = 0.0 Identities= 55/90 (61%), Positives = 70/90 (77%), Frame = +2 Query: 178PGGANNNNYANVELILDIAKRIPVQAVWAGWGHASENPKLPELLLKNGIAFMGPPSQAMW 237P G N NN+ANV+ IL  A +  V AVWAGWGHASENP LP  L  + IAF+GPP+ AM+ Sbjct:22886 PSGTNKNNFANVDEILKHAIKYEVDAVWAGWGHASENPDLPRRLNDHNIAFIGPPASAMF 23065Query: 238 ALGDKIASSIVAQTAGIPTLPWSGSGLRVD  267+LGDKIAS+I+AQT G+PT+ WSGSG+ ++ Sbjct: 23066SLGDKIASTIIAQTVGVPTVAWSGSGITME  23155 Trehelase >C23H3 Length = 39,721Minus Strand HSPs: Score = 227 (104.5 bits), Expect = 1.0e−95, Sun P (6)= 1.0e−95 Identities = 36/67 (53%), Positives = 51/67 (76%), Frame = −2Query: 2 VIKNLGYMVDNHGFVPNGGRVYYLTRSQPPLLTPMVYEYYMSTGDLDFVMEILPTLDKEY 61+I N  +++++ GFVPNGGRVYYL RSQPP   PMVYEYY++T  D+ V +++P ++KEY Sbjct: 9798MILNFAHIIETYGFVPNGGRVYYLRRSQPPFFAPMVYEYYLATQDIQLVADLIPVIEKEY 9619 Query:62 EFWIKNR  68  FW + R Sbjct: 9618 TFWSERR  9598 Score = 182 (83.8bits), Expect = 1.0e−95, Sum P (6) = 1.0e−95 Identities = 32/92 (34%),Positives = 55/92 (59%), Frame = −2 Query: 146MDSIRTWSIIPADLNAFMCANARILASLYEIAGDFKKVKVFEQRYTWAKREMRELHWNET 205+ +I T +I+P DLNAF+C N  I+   Y++ G+  K   +  R+T  +    ++ + Sbjct: 9372 ISTIETTNIVPVDLNAFLCYNMNIMQLFYKLTGNPLKHLEWSSRFTNFREAFTKVFYVPA 9193Query: 206 DGIWYDYDIELKTHSNQYYVSNAVPLYAKCYD  237   WYDY++   TH+  ++ SNAVPL+++CYD Sbjct: 9192RKGWYDYNLRTLTHNTDFFASNAVPLFSQCYD  9097 Score = 178 (81.9 bits), Expect= 1.0e−95, Sum P (6) = 1.0e−95 Identities = 37/102 (36%), Positives= 55/102 (53%), Frame = −2 Query: 246VHDYLERQGLLKYTKGLPTSLANSSTQQWDKENAWPPMIHMVIEGFRTTGDIKLMKVAEK 305V++ ++  G      G+PTS+    +QQWD  N W PM HM+IEG R + +  L + A Sbjct: 9069VYNEMQNSGAFSIPGGIPTSMNEETNQQWDFPNGWSPMNHMIIEGLRKSNNPILQQKAFT 8890 Query:306 MATSWLTGTYQSFIRTHAMFEKYNVTPHTEETSGGGGGEYEV  347+A  WL    Q+F  +  M+EKYNV     + + GG  E +V Sbjct: 8889LAEKWLETNMQTFNVSDEMNEKYNVKEPLGKLATGGEYEVQV  8764 Score = 169 (77.8bits), Expect = 1.0e−95, Sum P (6) = 1.0s−95 Identities = 29/58 (50%),Positives = 41/58 (70%), Frame = −2 Query: 84YQYKAKLKVPRPESYREDSELAEHLQTEAEKIQMWSEIASAAETGWDFSTRWFSQNGD 141+QY+ + + PRPES+RED   AEH  T+  K Q + ++ SAAE+GWDFS+RWF  + D Sbjct: 9546FQYRTEAETPRPESFREDVLSAEEFTTKDRKKQFFKDLGSAAESGWDFSSRWFKNHKD 9373 Score= 76 (35.0 bits), Expect = 1.0e−95, Sum P (6) = 1.0e−95 Identities= 13/21 (61%), Positives = 15/21 (71%), Frame = −1 Query: 348QTGFGWTNCVILDLLDKYGDQ 368 Q GFGWTNG  LDL+  Y D+ Sbjct: 8722QAGFGWTNGAALDLIFTYSDR 8660 Score = 45 (20.7 bits), Expect = 1.0e−95, SumP (6) = 1.0e−95 Identities = 10/24 (41%), Positives = 15/24 (62%), Frame= −1 Query: 371 SSSTASKFSFSLSNITFVVFILYI 394 +SS++S F +S       VF+LYISbjct: 8545 TSSSSSTFGYSNILTLITVFVLYI 8474 Score = 38 (17.5 bits), Expect= 2.6e−98, Sum P (7) = 2.6e−98 Identities = 7/7 (100%), Positives = 7/7(100%), Frame = −2 Query: 342 GGEYEVQ 348 GGEYEVQ Sbjct: 8787 GGEYEVQ8767 Score = 37 (17.0 bits), Expect = 1.6e−19, Sum 9 (4) = 1.6e−19Identities = 8/18 (44%), Positives = 10/18 (55%), Frame = −2 Query: 217KTHSNQYYVSNAVPLYAK 234 K++   YYVS   P Y K Sbjct: 30345KFTAEPYYVSRTPPRYEK 30292 >W05E10 Length = 31,273 Minus Strand ESFs:Score = 224 (103.1 bits), Expect = 7.0e−90, Sum 9 (7) = 7.0e−90Identities = 43/67 (64%), Positives = 49/67 (73%), Frame = −1 Query: 2VIKNLGYMVDNHGFVPNGGRVYYLTRSQPPLLTPMVYEYYMSTGDLDFVMEILPTLDKEY 61+I+NL  MVD +GFVPNCGRVYYL RSQPP L  MVYE Y+ T D  FV E+LPTL  KE Sbjct:28S57 MIRNLASMVDKYGFVPNGGRVYYLQRSQPPFLAAMVYELYEATNDKAFVAELLPTLLKEL 28778Query: 62 EFWIKNR  68  FW + R Sbjct: 28777 NFNNEKR  28757 Score = 192(88.4 bits), Expect = 7.0e−90, Sum 2 (7) = 7.0e−90 Identities = 31/84(36%), Positives = 52/84 (61%), Frame = −3 Query: 154IIPADLNAFMCANARILASLYEIAGDFKKVKVFEQRYTWAKREMRELHWNETDGIWYDYD 213++P DLN + C N  I + LYE  GD K  ++F  +    +  ++ + +N TDG WYDY+ Sbjct: 28427VLPVDLNGLLCNNMDIMEYLYEQIGDTKNSQIFENKRAIFRDTVQNVFYNRTDGTWYDYN 28248Query: 214 IELKTHSNQYYVSNAVPLYAKCYD  237 +  ++H+ ++Y S AVPL+  CY+ Sbjct:28247 LRTQSHNPRFYTSTAVPLFTNCYN  28176 Score = 125 (57.5 bits), Expect= 7.0e−90, Sum P (7) = 7.0e−90 Identities = 20/48 (41%), Positives= 30/48 (62%), Frame = −2 Query: 249YLERQGLLKYTKGLPTSLAMSSTQQWDKENAWPPMIHMVIEGFRTTGD 296+ ++ G+  Y  G+PTS++  S QQWD  N W P  HM+IEG R + + Sbjct: 28092FFQKMGVFTYPGGIPTSMSQESDQQWDFPNGWSPNNHMIIEGLRKSAN 27949 Score = 90 (41.4bits), Expect = 7.0e−90, Sum P (7) = 7.0e−90 Identities = 15/18 (83%),Positives = 18/18 (100%), Frame = −2 Query: 120 EIASAAETGWDFSTRWFS 137++ASAAE+GWDFSTRWFS Sbjct: 28566 DLASAAESGWDFSTRWFS 28513 Score = 89(41.0 bits), Expect = 7.0e−90, Sum P (7) = 7.0e−90 Identities = 18/40(45%), Positives = 24/40 (60%), Frame = −1 Query: 79KQFPYYQYKAKLKVPRPESYREDSELAEHLQTEAEKIQMW 118K F YQYK     VPRPESYRD++ +  L    A++ Q + Sbjct: 28732KSFKVYQYKTASNVPRPESYRVDTQNSAKLANGADQQQFY 28613 Score = 77 (35.4 bits),Expect = 7.0e−90, Sum P (7) = 7.0e−90 Identities = 14/21 (66%),Positives 16/21 (76%), Frame = −3 Query: 348 QTGFGWTNGVILDLLDKYGDQ 368Q GFGW+NG ILDLL  Y D+ Sbjct: 24395 QDGFGWSNGAILDLLLTYNDR 24333 Score= 51 (23.5 bits), Expect = 7.0e−90, Sum P (7) = 7.0e−90 Identities= 11/27 (40%), Positives = 16/27 (59%), Frame = −3 Query: 365YGDQFASSSTASKFSFSLSNITFVVFI 391 Y   FASSS AS   FS +++ F + + Sbjct: 2846YN*PFASSSDASSCPFSTNSVIFSILV 2766 Score = 41 (18.9 bits), Expect= 3.3e−93, Sum P (8) = 3.3e−93 Identities = 7/9 (77%), Positives = 8/9(88%), Frame = −2 Query: 340 GGGGEYEVQ 348 G GGEY+VQ Sbjct: 24468GSGGEYDVQ 24442 Score = 39 (18.0 bits), Expect = 2.0e−37, Sum P (5)= 2.0e−37 Identities = 7/14 (50%), Positives = 8/14 (57%), Frame = −2Query: 221 NQYYVSNAVPLYAK 234 N YY+   V LY K Sbjct: 4524 NHYYIIQMVSLYTI4483 Score = 38 (17.5 bits), Expect = 4.0e−88, Sum P (7) = 4.0e−88Identities = 11/30 (36%), Positives = 13/30 (43%), Frame = −1 Query: 367DQFASSSTASKFSFSLSNITFVVFILYIFS 396 DQF  S   SKFS     + F      +FS Sbjct:7588 DQFVISFICSKFSSKNKKLYFCPSHFSLFS 7499

Gene fusions to GFP may also be constructed using, for example, theisocitrate dehydrogenase and isocitrate lyase genes to test fortransition to the glyoxylate cycle for the generation of glucose fromfatty acid metabolism during dauer arrest and recovery. Moreover, genefusions to hexokinase and glucose metabolism genes may be used test forthe switch to sugar based metabolism during reproductive development.

GFP fusions to these genes are expected to be transcriptionallyregulated depending on whether the animal is in fat storage, fatbreakdown, glycogen storage, or glycogen breakdown, trehalose storage,or trehalose breakdown metabolic states. Drugs that perturb theexpression of these genes may regulate transcriptional regulatoryproteins like DAF-3, DAF-12, and DAF-16 that may regulate batteries ofsuch metabolic genes. The GFP reporter genes provide a screen forperturbations of these regulatory genes. In addition, GFP fusions to thefull length proteins may also reveal subcellular localization, forexample, of fat storage proteins to fat droplets and regulation of thelocalization of these proteins. Drugs that perturb the localization ofthese fusion proteins may also be potent regulators of fat metabolismand may be used to treat obesity and diabetes.

Daf12-GFP Fusions

Daf-12 expression has been examined using a full length, rescuing GFPfusion to daf-12. We have found that the gene is expressed in a smallnumber of neurons in wild type animals, and many more in a daf-2, daf-7,or pheromone induced dauer. Thus, the daf-12 expression pattern istranscriptionally regulated by the daf pathway, perhaps by DAF-2 orDAF-16. We have also observed DAF-12/GFP expression in hypodermal cellsat the L2 and later stages, showing that daf-12 is a stage specific geneactivity in this tissue. This is consistent with the heterochroniceffects of weak daf-12 mutations.

This daf-12-GFP fusion also allowed us to view the dynamic regulation ofdaf-12 gene action during insulin and TGF-β regulated dauer orreproductive development. daf-12 encodes a nuclear hormone receptor mostclosely related to the mammalian vitamin D and thyroid hormonereceptors. We believe that the ligand for DAF-12 is likely to beregulated by insulin like or TGF-β daf gene signaling. That ligand maybe produced by the C. elegans equivalent to the thyroid gland, which maybe related to the subesophogeal glands of insects. For example, neuronsin the retrovesicular ganglion of C. elegans may produce the daf-12ligand under DAF-16 and DAF-3 control. The mapping of exactly whichneurons the daf-2 and age-1 gene products function to regulate dauerarrest will identify the neuron. To identify the genes regulated by theDAF-16 and DAF-3 transcription factors, a yeast one hybrid experimentmay be used (as described herein). GFP fusion to the genes so revealedshould show that they are expressed in the key DAF-12 ligand producingneuron and are responsive to daf-3 and daf-16 mutations.

C. elegans

In one working example, the above-described reporter gene construct isintroduced into wild-type C. elegans according to standard methods knownin the art. If the enhancer element is operational, then it is expectedthat reporter gene expression is turned on. Alternatively, in dafmutants (e.g., daf-7 or daf-2 mutants, where insulin signaling isdefective) carrying the above-described reporter gene construct,reporter gene activity is turned off.

Using this on/off distinction, test compounds or extracts are evaluatedfor the ability to disrupt the signaling pathways described herein. Inone working example, daf-2 mutant worms carrying the reporter geneconstruct are used to assay the expression of the reporter gene. Themajority of worms expressing the reporter gene will arrest at the dauerstage because of the daf-2 phenotype. If however the test compound orextract inhibits DAF-16 activity, then the worms will exhibit a daf-2;daf-16 phenotype (i.e., do not arrest), developing to produce eggs. Sucheggs are selected using a bleach treatment and reporter gene expressionin the test compound or extract is assayed according to standardmethods, e.g., worms are examined with an automated fluorometer toreveal the presence of reporter gene expression, e.g., GFP. Candidatecompounds that suppress the daf-2 phenotype or turn on reporter geneexpression, i.e., activate signals in the absence of DAF-2 receptor(e.g., PIP3 mimetics) or inactivate DAF-16, are considered useful in theinvention.

Analogous screens may also be performed using daf-7 mutants as a meansto identify drugs that inactivate other daf-genes, such as DAF-3, orcompounds that activate the DAF-1/DAF-4 receptors. Such screens may becoupled to reporter screens, for example, using GFP reporter genes whoseexpression is under DAF-3 transcriptional control (e.g., the myoIIelement). Drugs identified in such screens are useful as DAF-7 mimetics.Because DAF-7 expression may be down regulated in obesity, such drugsare useful in the treatment of obesity induced Type II diabetes

In yet another working example, C. elegans DAF-3 and DAF-16 genes can bereplaced with a human homolog, (e.g., FKHR or FKHRL1 for DAF-16), andscreens similar to those described above performed in the nematodesystem. Because drugs may act upstream of the transcription factors, itis useful to replace DAF-1, DAF-4, DAF-8,DAF-14, DAF-2, DAF-3, DAF-16,or AGE-1 with the appropriate human homolog, and to screen the humanizedC. elegans animals. Such screens are useful for identifying compoundshaving activities in humans.

Mammalian Cells

Mammalian insulin-responsive cell lines are also useful in the screeningmethods of the invention. Here reporter gene constructs (for example,those described above) are introduced into the cell line to evaluate theability of a test compound or extract to modulate insulin and TGF-βsignaling pathways using a second construct expressing a C. elegans dafage, or akt gene or their corresponding human homologs. Exemplary celllines include, but are not limited to, mouse 3T3, L6, and L1 cells(MacDougald et al., Ann. Rev. Biochem. 64: 345–373, 1995) Introductionof the constructs into such cell lines is carried out according tostandard methods well known in the art.

To test a compound or extract, it is added to the cell line, andreporter gene expression is monitored. Compounds that induce reportergene expression in the absense of insulin or DAF-7 signaling areconsidered useful in the invention. Such compounds may also turn thecells into adipocytes, as insulin does.

Compounds identified in mammalian cells may be tested in other screeningassays described herein, and, in general, test compounds may be assayedin multiple screens to confirm involvement in insulin or DAF-7signaling.

Metabolic control by DAF-7 protein may be tested using any known cellline, e.g., those described herein.

In Vitro Screening Methods

A variety of methods are also available for identifying useful compoundsin in vitro assays. In one particular example, test compounds arescreened for the ability to activate the phosphorylation of Smadproteins, DAF-8, DAF-14, or DAF-3, by DAF-1 or DAF-4 in vitro. In theseassays, DAF-8, DAF-14, or DAF-3 is preferably tagged with a heterologousprotein domain, for example, the myc epitope tag domain(s) by the methodof Ausubel et al., and are incubated with the C-terminal kinase domainof DAF-1 or DAF-4. Phosphorylation of the Smad proteins is preferablydetected by immunoprecipitation using antibodies specific to the tag,followed by scintillation counting. Test compounds may be screened inhigh throughout microtiter plate assays. A test compound thateffectively stimulates the phosphorylation of DAF-8, DAF-14, or DAF-3 isconsidered useful in the invention. Using these same general assays,compounds that activate the phosphorylation of DAF-16 by AKT or GSK-3may also be identified.

In another working example, test compounds are screened for the abilityto inhibit the in vitro association of DAF-16 and the Smad proteinsDAF-3, or to preferentially activate the association of DAF-16 withDAF-8 or DAF-14, or to inhibit the association of DAF-3 and DAF-16 withDNA in vitro. These assays are carried out by any standard biochemicalmethods that test protein-protein binding or protein-DNA binding. In oneparticular example, to test for interactions between proteins, eachprotein is tagged with a different heterologous protein domain (asdescribed above). Immunoprecipitations are carried out using an antibodyto one tag, and an ELISA assay is carried out on the immunoprecipitationcomplex to test for the presence of the second tag. In addition, ifinteraction capability is enhanced by a DAF or AKT kinase, this proteinis also preferably included in the reaction mixture. Similarly, to testfor interactions of these proteins with DNA, antibodies to the tag areutilized in immunoprecipitations, and the presence of the DNA detectedby the presence of the DNA label in the immunoprecipitation complex. Atest compound that effectively inhibits the association between theseproteins or between DAF-3 and DAF-16 with DNA or both is considereduseful in the invention.

In still another working example, test derivatives of PIP3 are screenedfor the ability to increase in vitro AKT activity. This is accomplished,in general, by combining a labeled PIP3 and an AKT polypeptide in thepresence and absence of the test compound under conditions that allowPIP3:AKT to bind in vitro. Compounds are then identified that interferewith the formation of the PIP3:AKT complex. Test compounds that passthis first screen may then be tested for increased AKT activation invitro using GSK3 targets, or may be tested in nematodes or mammaliancells (as described above). An increase in AKT kinase activity is takenas an indication of a compound useful for ameliorating or delaying animpaired glucose tolerance condition.

In yet another working example, DAF-3 or DAF-16 may be expressed in ayeast one-hybrid assay for transcriptional activation. Methods for suchassays are described in Brent and Ptashne (Cell 43:729–736, 1985). Atest compound that blocks the ability of DAF-3 or DAF-16 or both toactivate (or repress) transcription in this system is considered usefulin the invention.

In a final working example, compounds may be screened for their abilityto inhibit an interaction between any of DAF-3, DAF-8, and DAF-14, orbetween DAF-3 and DAF-16. These in vivo assays may be carried out by any“two-hybrid” or “interaction trap” method (for example, by using themethods described by Vijaychander et al (Biotechniques 20: 564–568)).

Screens for Isolating Longevity Therapeutics

The worm insulin signaling pathway has been implicated in longevitycontrol of C. elegans. Drugs which perturb this pathway could affectlifespan. Specifically, inhibition of the pathway would be expected toextend lifespan. Drugs that inactivate the DAF-2 ligands, the AGE-1 PI3kinase, or decrease PIP3 signals in any way, for example, by increasingDAF-18/PTEN activity, decreasing PDK or AKT activity, or decreasing thephosphorylation of DAF-16, are expected to increase longevity. Suchdrugs may be used topically on the skin to increase longevity in thisorgan. It is significant that AGE-1 generates a second messenger, PIP3,that directly regulates AKT and perhaps PDK activity. Antagonists toPIP3 are expected to extend lifespan, but any drug that mimics theactivity state of the pathway during aging is expected to increaselongevity. For example, drugs causing low activity of the followingproteins: DAF-2 agonist, DAF-2 receptor, AGE-1, PDK, and AKT, wouldincrease longevity. Drugs causing high activity of PTEN or DAF-16 (highmeaning unphosphorylated) would increase longevity.

The insulin-like signaling genes that function in metabolic regulationand molting control also function to control aging in the animal. Wehave shown that declines in daf-2 insulin receptor-like age-1 PI-3kinase, PDK-1, and akt-1/2 signaling cause dauer arrest and acorresponding increase in lifespan and a change in metabolism towardsfat storage. Thus, drugs that perturb the gene activities in thispathway are expected to regulate longevity as well as metabolism.Specifically, chemicals that decrease the activity of the humanhomologues of the DAF-2 insulin/IGF-I receptor homologue, decrease theactivity of the human homologue of the AGE-1/PI3 kinase, decrease theactivity of human homologues of AKT-1 and AKT-2, decrease the activityof the human homologue of PDK-1, or inhibit the phosphorylation of thehuman homologues of DAF-16 by the human homologues of AKT-1 and AKT-2increase longevity. Chemicals that increase the activity of DAF-18 PTENalso increase longevity, since decreases in DAF-18 activity decreaselongevity.

Similarly, the AGE-1 and AKT-1/2 proteins are enzymes with in vitroactivities. An AGE-1 assay preferably involves phophorylation of aphosphatidyl inositol target on the 3 position. The AKT-1 or AKT-2kinase assay involves phosphorylation of DAF-16 as well as the humanDAF-16 homologues, FKHR, FKHRL1, and AFX targets. Chemical screens fordrugs that inhibit in vitro activities of the human homologues of theseC. elegans kinases are first preferably performed in vitro. Chemicalsthat perturb this function are then tested on C. elegans mutantscarrying the human gene as the only functional copy of the gene. Ifdesired, positive drugs could then be tested on mice for those thatincrease longevity.

Screens for Identifying Pesticide and Nematicide Compounds

Our discovery that converging insulin-like and DAF-7 TGF-β likeneuroendocrine signals regulate diapause arrest in C. elegans is alsoimportant for the development of novel nematicides and pesticides. Forexample, the finding that insulin like signaling regulates metabolism inanimals as phylogenetically distant as nematodes and mammals suggeststhat this pathway was present in the common ancestor of worms andmammals over 600,000,000 years ago. Diapause, the suspension ofdevelopment by environmental signals, is phyletically general. In viewof the results described herein, insulin may regulatediapause/developmental arrest in many animals, including insects andother nematodes. In fact, human insulin induces recovery of diapausingcorn borers, and a cholinergic neuronal input to dauer arrest has beenshown herein to exist in both C. elegans and the mammalian parasiticnematode Ancylostoma caninum. These observations indicate that dafpathway results from C. elegans can be generalized to distant nematoderelatives as well as other invertebrates, most importantly, insects.Since diapause is a non feeding state, novel insecticides andnematicides may be developed which induce diapause if the insulin likepathway can be inactivated in insects or nematodes. Specifically, drugsthat induce downregulation of the insect or parasitic nematodehomologues of DAF-2, AGE-1, PDK-1, AKT-1, or AKT-2, or upregulation ofDAF-18 or DAF-16 would induce non feeding diapause. Such an agent wouldbe expected to protect crops from destruction by feeding and infection.In addition, agents that induce activity of DAF-2, AGE-1, PDK-1, AKT-1,or AKT-2, or downregulation of DAF-18 or DAF-16 would be expected toinduce recovery from diapause. Since diapause is an overwintering stressresistant state, and is generally the infective stage of plant andanimal parasitic nematodes, such agents would improve pest infestationsby perturbing the overwintering or infective process.

Modulatory Compounds

Our experimental results facilitate the isolation of compounds useful inthe treatment of impaired glucose tolerance diseases that areantagonists or agonists of the insulin or TGF-β signaling pathwaysidentified in C. elegans and described above. Exemplary methods for theisolation of such compounds now follow.

Antagonists

As discussed above, useful therapeutic compounds include those whichdown regulate the expression or activity of DAF-3, DAF-16, or DAF-18(PTEN). To isolate such compounds, DAF-3, DAF-16, or DAF-18 (PTEN)expression is measured following the addition of candidate antagonistmolecules to a culture medium of DAF-3, DAF-16, or DAF-18 (PTEN)expressing cells. Alternatively, the candidate antagonists may bedirectly administered to animals (for example, nematodes or mice) andused to screen for their effects on DAF-3, DAF-16, or DAF-18 (PTEN)expression.

DAF-3, DAF-16, or DAF-18 (PTEN) expression is measured, for example, bystandard Northern blot analysis (Ausubel et al., supra) using a DAF-3,DAF-16, or DAF-18 (PTEN) nucleic acid sequence (or fragment thereof) asa hybridization probe. The level of DAF-3, DAF-16, or DAF-18 (PTEN)expression in the presence of the candidate molecule is compared to thelevel measured for the same cells, in the same culture medium, or in aparallel set of test animals, but in the absence of the candidatemolecule. Preferred modulators for anti-diabetic or anti-obesitypurposes are those which cause a decrease in DAF-3, DAF-16, or DAF-18(PTEN) expression.

Alternatively, the effect of candidate modulators on expression oractivity may be measured at the level of DAF-3, DAF-16, or DAF-18 (PTEN)protein production using the same general approach in combination withstandard immunological detection techniques, such as Western blotting orimmunoprecipitation with a DAF-3, DAF-16, or DAF-18 (PTEN) specificantibody (for example, the DAF-3 or DAF-16 antibodies described herein).Again, useful anti-diabetic or anti-obesity therapeutic modulators areidentified as those which produce a decrease in DAF-3, DAF-16, or DAF-18(PTEN) polypeptide production. Antagonists may also affect DAF-3,DAF-16, or DAF-18 (PTEN) activity without any effect on expressionlevel. For example, the identification of kinase cascades upstream ofDAF-3 and DAF-16 (as described herein) suggest that the phosphorylationstate of these polypeptides is correlated with activity. Phosphorylationstate may be monitored by standard Western blotting using antibodiesspecific for phosphorylated amino acids. In addition, because DAF-3 andDAF-16 are transcription factors, reporter genes bearing operably linkedDAF-3 or DAF-16 binding sites (for example, the myoII enhancer element)may be used to directly monitor the effects of antagonists on DAF-3 orDAF-16 gene activity.

Candidate modulators may be purified (or substantially purified)molecules or may be one component of a mixture of compounds (e.g., anextract or supernatant obtained from cells). In a mixed compound assay,DAF-3, DAF-16, or DAF-18 (PTEN) expression is tested againstprogressively smaller subsets of the candidate compound pool (e.g.,produced by standard purification techniques, e.g., HPLC or FPLC;Ausubel et al., supra) until a single compound or minimal compoundmixture is demonstrated to modulate DAF-3, DAF-16, or DAF-18 (PTEN)expression.

Candidate DAF-3, DAF-16, or DAF-18 (PTEN) antagonists include peptide aswell as non-peptide molecules (e.g., peptide or non-peptide moleculesfound, e.g., in a cell extract, mammalian serum, or growth medium onwhich mammalian cells have been cultured).

Antagonists found to be effective at the level of cellular DAF-3,DAF-16, or DAF-18 (PTEN) expression or activity may be confirmed asuseful in animal models (for example, nematodes or mice). For example,the compound may ameliorate the glucose intolerance and diabeticsymptoms of mouse models for Type II diabetes (e.g., a db mouse model),mouse models for Type I diabetes, or models of streptozocin-induced βcell destruction.

A molecule which promotes a decrease in DAF-3, DAF-16, or DAF-18 (PTEN)expression or DAF-3, DAF-16, or DAF-18 (PTEN) activity is consideredparticularly useful in the invention; such a molecule may be used, forexample, as a therapeutic to decrease the level or activity of native,cellular DAF-3, DAF-16, or DAF-18 (PTEN) and thereby treat a glucoseintolerance condition in an animal (for example, a human).

If desired, treatment with an antagonist of the invention may becombined with any other anti-diabetic or anti-obesity therapies.

Agonists

Also as discussed above, useful therapeutic compounds are those which upregulate the expression or activity of DAF-1, DAF-2, DAF-4, DAF-7,DAF-8, DAF-11, DAF-14, AGE-1, AKT, COD-5, or PDK-1. To isolate suchcompounds, expression of these genes is measured following the additionof candidate agonist molecules to a culture medium of DAF-1, DAF-2,DAF-4, DAF-7, DAF-8, DAF-11, DAF-14, AGE-1, AKT, COD-5, or PDK-1expressing cells. Alternatively, the candidate agonists may be directlyadministered to animals (for example, nematodes or mice) and used toscreen for effects on DAF-1, DAF-2, DAF-4, DAF-7, DAF-8, DAF-11, DAF-14,AGE-1, AKT, COD-5, or PDK-1 expression.

DAF-1, DAF-2, DAF-4, DAF-7, DAF-8, DAF-11, DAF-14, AGE-1, AKT, COD-5, orPDK-1 expression is measured, for example, by standard Northern blotanalysis (Ausubel et al., supra) using all or a portion of one of thesegenes as a hybridization probe. The level of DAF-1, DAF-2, DAF-4, DAF-7,DAF-8, DAF-11, DAF-14, AGE-1, AKT, COD-5, or PDK-1 expression in thepresence of the candidate molecule is compared to the level measured forthe same cells, in the same culture medium, or in a parallel set of testanimals, but in the absence of the candidate molecule. Preferredmodulators for anti-diabetic or anti-obesity purposes are those whichcause an increase in DAF-1, DAF-2, DAF-4, DAF-7, DAF-8, DAF-11, DAF-14,AGE-1, AKT, COD-5, or PDK-1 expression.

Alternatively, the effect of candidate modulators on expression may bemeasured at the level of DAF-1, DAF-2, DAF-4, DAF-7, DAF-8, DAF-11,DAF-14, AGE-1, AKT, COD-5 or PDK-1 protein production using the samegeneral approach in combination with standard immunological detectiontechniques, such as Western blotting or immunoprecipitation with anappropriate antibody. Again, the phosphorylation state of thesepolypeptides is indicative of DAF activity and may be measured onWestern blots. Useful anti-diabetic or anti-obesity modulators areidentified as those which produce an increase in DAF-1, DAF-2, DAF-4,DAF-7, DAF-8, DAF-11, DAF-14, AGE-1, AKT, COD-5, or PDK-1 polypeptideproduction.

Candidate modulators may be purified (or substantially purified)molecules or may be one component of a mixture of compounds (e.g., anextract or supernatant obtained from cells). In a mixed compound assay,DAF-1, DAF-2, DAF-4, DAF-7, DAF-8, DAF-11, DAF-14, AGE-1, AKT, COD-5, orPDK-1 expression is tested against progressively smaller subsets of thecandidate compound pool (e.g., produced by standard purificationtechniques, e.g., HPLC or FPLC; Ausubel et al., supra) until a singlecompound or minimal compound mixture is demonstrated to modulate DAF-1,DAF-2, DAF-4, DAF-7, DAF-8, DAF-11, DAF-14, AGE-1, AKT, COD-5, or PDK-1expression.

Alternatively, or in addition, candidate compounds may be screened forthose which agonize native or recombinant DAF-1, DAF-2, DAF-4, DAF-7,DAF-8, DAF-11, DAF-14, AGE-1, AKT, COD-5, or PDK-1 activities. In oneparticular example, DAF-1 and DAF-4 phosphorylation of DAF-8 and DAF-14,or AKT phosphorylation of DAF-16, may be activated by agonists.

Candidate DAF-1, DAF-2, DAF-4, DAF-7, DAF-8, DAF-11, DAF-14, AGE-1, AKT,COD-5, or PDK-1 agonists include peptide as well as non-peptidemolecules (e.g., peptide or non-peptide molecules found, e.g., in a cellextract, mammalian serum, or growth medium on which mammalian cells havebeen cultured).

Agonists found to be effective at the level of cellular DAF-1, DAF-2,DAF-4, DAF-7, DAF-8, DAF-11, DAF-14, AGE-1, AKT, COD-5, or PDK-1expression or activity may be confirmed as useful in animal models (forexample, nematodes or mice).

A molecule which promotes an increase in DAF-1, DAF-2, DAF-4, DAF-7,DAF-8, DAF-11, DAF-14, AGE-1, AKT, COD-5, or PDK-1 expression oractivities is considered particularly useful in the invention; such amolecule may be used, for example, as a therapeutic to increase thelevel or activity of these native, cellular genes and thereby treat aglucose intolerance condition.

If desired, treatment with an DAF-1, DAF-2, DAF-4, DAF-7, DAF-8, DAF-11,DAF-14, AGE-1, AKT, COD-5, or PDK-1 agonist may be combined with anyother anti-diabetic or anti-obesity therapies.

Animal Model Systems

Compounds identified as having activity in any of the above-describedassays are subsequently screened in any number of available diabetic orobesity animal model systems, including, but not limited to ob (Coleman,Dibetologia 14: 141–148, 1978; Chua et al., Science 271: 994–996, 1996;Vaisse et al., Nature Genet. 14:95–100, 1996), db (Chen et al., Cell 84:491–495, 1996), agouti mice, or fatty rats (Takaga et al. Biochem.Biophys. Res. Comm. 225: 75–83, 1996). Test compounds are administeredto these animals according to standard methods. Additionally, testcompounds may be tested in mice bearing knockout mutations in theinsulin receptor, IGF-1 receptor (e.g., Liu et al., Cell 75:59–72,1993), IR-related receptor, DAF-7 homolog, or any of the daf (FKHR,FKHRL1, AFX) genes described herein. Compounds can also be tested usingany standard mouse or rat model of Type I diabetes, e.g., a streptozinablated pancreas model.

In one particular example, the invention involves the administration ofDAF-7 or its homolog as a method for treating diabetes or obesity.Evaluation of the effectiveness of such a compound is accomplished usingany standard animal model, for example, the animal diabetic modelsystems described above. Because these mouse diabetic models are alsoassociated with obesity, they provide preferred models for human obesityassociated Type II diabetes as well. Such diabetic or obese mice areadministered C. elegans or human DAF-7 according to standard methodswell known in the art. Treated and untreated controls are then monitoredfor the ability of the compound to ameliorate the symptoms of thedisease, e.g., by monitoring blood glucose, ketoacidosis, andatherosclerosis. Normalization of blood glucose and insulin levels istaken as an indication that the compound is effective at treating aglucose intolerance condition.

Therapy

Compounds of the invention, including but not limited to, DAF-7 and itshomologs, and any antagonist or agonist therapeutic agent identifiedusing any of the methods disclosed herein, may be administered with apharmaceutically-acceptable diluent, carrier, or excipient, in unitdosage form. Conventional pharmaceutical practice may be employed toprovide suitable formulations or compositions to administer suchcompositions to patients. Although intravenous administration ispreferred, any appropriate route of administration may be employed, forexample, parenteral, subcutaneous, intramuscular, intracranial,intraorbital, ophthalmic, intraventricular, intracapsular, intraspinal,intracisternal, intraperitoneal, intranasal, aerosol, or oraladministration. Therapeutic formulations may be in the form of liquidsolutions or suspensions; for oral administration, formulations may bein the form of tablets or capsules; and for intranasal formulations, inthe form of powders, nasal drops, or aerosols.

Methods well known in the art for making formulations are found in, forexample, “Remington's Pharmaceutical Sciences.” Formulations forparenteral administration may, for example, contain excipients, sterilewater, or saline, polyalkylene glycols such as polyethylene glycol, oilsof vegetable origin, or hydrogenated napthalenes. Biocompatible,biodegradable lactide polymer, lactide/glycolide copolymer, orpolyoxyethylene-polyoxypropylene copolymers may be used to control therelease of the compounds. Other potentially useful parenteral deliverysystems for antagonists or agonists of the invention includeethylene-vinyl acetate copolymer particles, osmotic pumps, implantableinfusion systems, and liposomes. Formulations for inhalation may containexcipients, for example, lactose, or may be aqueous solutionscontaining, for example, polyoxyethylene-9-lauryl ether, glycocholateand deoxycholate, or may be oily solutions for administration in theform of nasal drops, or as a gel.

DAF polypeptides are administered at any appropriate concentration, forexample, for DAF-7, at a concentration of around 10 nM.

Pedigree Analysis and Genetic Testing

The discovery described herein that DAF polypeptides are involved inglucose metabolism enables assays for genetic testing to identify thoseindividuals with predispositions toward the development of glucoseintolerance conditions, such as diabetes or obesity, by determining thepresence of a mutation found in a human gene having identity to any ofthe C. elegans daf-1, daf-2, daf-3, daf-4, daf-7, daf-8, daf-11, daf-14,daf-16, age-1, akt, daf-18 (PTEN), or pdk-1 genes. In one embodiment,the development of this testing method requires that the individual be amember of a family that has multiple affected and unaffected memberscarrying one mutation from the list of above-listed genes. Those skilledin the art will understand that a diabetic or obesity phenotype may beproduced by daf, age, or akt mutations found on different chromosomes,and that low resolution genetic mapping of the diabetic condition insingle family pedigrees will be sufficient to favor some daf, age, orakt genes over others as causing the glucose intolerance condition in aparticular pedigree. In one particular example, mutations associatedwith glucose intolerance may be found in different genes in, forexample, the DAF-7 signaling pathway in each pedigree. In addition,because mutations in a common pathway can show complex geneticinteractions, multiple DAF mutations may segregate in single pedigress.These mutations can behave recessively in some genetic backgrounds anddominantly in others.

Those skilled in the art further understand that, to determine diseaselinkage with a chromosomal marker, it may be necessary to evaluate theassociation of inheritance patterns of several different chromosomalmarkers (for example, from the collection of highly polymorphic mappedDNA allelic variants) in the genomic DNAs of family members and of theclinically affected individuals. Methods commonly used in determiningsegregation patterns of human genetic diseases are well known in theart. In addition, methods are known in the art for determining whetherindividuals in a family are useful for providing information todetermine co-segregation of an allele with a glucose intolerance trait.

Here, fragments of genomic DNA (e.g., RFLP fragments) are prepared fromeach of the available members of the family, and each distinctive DNAallelic variant of the polymorphic chromosome marker within the familyis evaluated to determine which polymorphisms (i.e., chromosomal region)is linked with the glucose intolerance phenotype within a particularfamily. It is preferred that the parents of the marker individual beheterozyous for a DNA allelic variant so that the segregation pattern ofthe DNA allelic variant linked with the diabetic or obese phenotype inthe marker can be recognized. The inheritance of the diabetic phenotypecan be judged to be dominant or recessive, depending on the pattern ofinheritance. Most diabetes is dominantly inherited, and therefore inbredpedigrees are generally not necessary in the etiology of the diabeticcondition.

With respect to Type II diabetes, the highest rate of this kind ofdiabetes in the world is found in American Indians of the Pima tribe.Such families are useful for mapping one particular cause of diabetes,but, in general, diabetes is caused by mutations in a variety of genes,including daf genes. Thus, by testing for low resolution linkage to acandidate daf, age, or akt mutation, and then by sequencing theparticular linked daf gene in affected and unaffected individuals, aparticular daf mutation can be associated with a particular diabeticpedigree.

Human DAF homologues are mapped to chromosome regions using standardmethods. For example, the probable DAF-16 homologues FKHR and FKHRL1 arelocated on chromosomes 13 and 11, respectively, and AFX is located onthe X chromosome. In particular, candidate loci for human DAF homologuesare as follows: P85=5q13, P110alpha=3q26.3, PTEN=10q23.3, Akt-1=14q32.3,Akt-2=19q13.1, FKHRL1=11q23, FKHR=13q14.1, Afx=xq13.1, and Daf-7(GDF-8)=2q32.1 (the position at which NIDDM1 has been mapped).

Any daf akt, or age genes mapping to the approximate chromosomal regionsassociated with diabetes or glucose intolerance are sequenced fromaffected and unaffected individuals. Preferably, at least two genes perpedigree of 5–20 affected (and unaffected controls) are sequenced. Thedaf genomic regions are PCR amplified and compared between affected andunaffected DNA samples. Mutations detected in affected individuals areexpected to (but need not) map to conserved domains of the DAF genes.Because it is known that not all carriers of known diabetes-inducingmutations show metabolic defects, we expect that some non-diabeticnon-glucose intolerant family members will carry the same daf mutationas affected family members. For this reason, a correlation of affectedfamily members with a daf mutation is more important than a correlationof nonaffected with no mutation. Those skilled in the art will know thatphenotypic classification of affected and unaffected individuals cangreatly enhance the power of this genetic analysis (Nature Genet. 11:241–247, 1995). In addition, other mutations in the same daf gene areexpected in some but not all diabetic pedigrees. For dominant diabeticinheritance, the affected individuals carry a daf, age, or akt mutationas well as a normal allele. For recessive diabetic inheritance,individuals carry two daf mutations that may be identical or twoindependent mutations in the same gene. In addition, some diabeticindividuals may carry mutations in more than one daf, age, or akt gene(so called non-allelic non-complementation).

It is routine in the art of genetic counseling to determine risk factorsgiven the presence of a closely linked molecular genetic marker in thegenomic DNA of the individual and when combined with the additionalunderstanding provided by the pedigree of the individual in the family.For example, a risk factor may be calculated for an individual in anage, akt, or daf chromosome family in a manner similar to thosedescribed for assessing the risk of other commonly known geneticdiseases that are known to run in families, e.g., Huntington's diseaseand cystic fibrosis.

Once mutations in daf akt, or age genes are associated with diabetes ina pedigree analysis, diagnostic PCR sequencing of these daf genes can beused to diagnose glucose intolerant, prediabetic, diabetic, obesity, andatherosclerotic conditions. Preferably, the daf akt, or age gene regionsare PCR amplified from patients and mutations detected in the daf genesusing standard DNA sequencing or oligonucleotide hybridizationtechniques. The use of such gene sequences or specific antibody probesto the products of these sequences provide valuable diagnostics,particularly in view of the likelihood there exist two classes of typeII diabetics: those with defects in the TGF-β signaling genes, and thosewith defects in insulin signaling genes. Such genetic tests willinfluence whether drugs that affect DAF-7 TGF-β or DAF-2 insulin likesignals are prescribed.

To carry out the above analysis (as well as the other screening,diagnostic, and therapeutic methods described herein), mammalianhomologs corresponding to the C. elegans daf-1, age-1, daf-4, daf-8, anddaf-7 genes are isolated as described above for daf-2, daf-3, anddaf-16. Again, standard hybridization or PCR cloning strategies areemployed, preferably utilizing conserved DAF, AGE, or AKT motifs forprobe design followed by comparison of less conserved sequences flankingthese motifs. Exemplary motifs for these genes are as follows:

DAF-1 (139 amino acid motif) (SEQ ID NO: 13)   274TSGSGMGPTTLHKLTIGGQIRLTGRVGSGRFGNVSRGDYRGEAVAVKVFNALDEPAFHKETEIFETRMLRHPNVLRYIGSDRVDTGFVTELWLVTEYHPSGSLIIDFLLENTVNIETYYNLMRSTASGLAFL HNQIGGSK  412 DAF-1 (62amino acid motif) (SEQ ID NO: 14)   450EDAASDIIANENYKCGTVRYLAPEILNSTMQFTVFESYQCADVY SFSLVMWETLCRCEDGDV  511DAF-1 (31 amino acid motif) (SEQ ID NO: 15)   416KIPAMAIIRDIKSKNIMVKNDLTCAIGDLGLSL  466 DAF-1 (72 amino acid motif) (SEQID NO: 16)   520 IPYIEWTDRDPQDAQMFDVVCTRRLRPTENPLWKDHPEMIKHIMEIIKTCWNGNPSARFTS YICRKRMDERQQ  591 AGE-1 (150 amino acid motif) (SEQ IDNO: 17)   991 YFESVDRFLYSCVGYSVATYIMGIKDRHSDNLMLTEDGKYVIIIDFGHILGHGKTKLGIQRDRQPFILTEHFMTVIRSGKSVDGNSHELQKFKTLCVEAYEVMWNNRDLFVSLFTLMLGMELPELSTKADLD HLKKTLFCNGESKEEARKF  1140AGE-1 (113 amino acid motif) (SEQ ID NO: 18)   826SPLDPVYKLGEMIIDKAIVLGSAKRPLMLHWKNKNPKSDLHLPFCAMIFKNGDDLRQDMLVLQVLEVMDNIWKAANIDCCLNPYAVLPMGEMIGIIEVVPNCKTIFEIQVGTG  938 AGE-1 (106 amino acid motif) (SEQ ID NO:19)   642 LAFVWTDRENFSELYVMLEKWKPPSVAAALTLLGKRCTDRVIRKFAVEKLNEQLSPVTFHLFILPLIQALKYEPRAQSEVGMMLLTRA LCDYRIGNRLFWLLRAEI  747AGE-1 (60 amino acid motif) (SEQ ID NO: 38)    91EIKLSDFKHQLFELIAPMKWGTYSVKPQDYVFRQLNNFGEIEVI FNDDQPLSKLELHGTF  150 AKT(121 amino acid motif) (SEQ ID NO: 60) 33685QVLDDHDYGRCVDWWGVGVVMYEMMCGRLPFYSKDHNKLFELIMAGDLRFPSKLSQEARTLLTGLLVKDPTQRLGGGPEDALEICRADFFRTVDWEATYRKEIEPPYKPNVQSETDTSYFD  34047 AKT (66 amino acid motif) (SEQID NO: 61) 32314 TMEDFDFLKVLGKGTFGKVILCKEKRTQKLYAIKILKKDVIIAREEVAIITLTENRVLQRCKHPFLT  32511 AKT (45 amino acid motif) (SEQ ID NO: 62)33509 KLENLLLDKDGHIKIADFGLCKEEISFGDKTSTFCGTPEYLAPE V  33643 AKT (57amino acid motif) (SEQ ID NO: 63) 32667YFQELKYSFQEQHYLCFVMQFANGGELFTHVRKCGTFSEPRARF YGAEIVLALGYLH  32837 AKT(59 amino acid motif) (SEQ ID NO: 64) 31846STFAIFYFQTMLFEKPRPNMFMVRCLQWTTVIERTFYAESAEVR QRWIHAIESISKKYK  32022 AKT(33 amino acid motif) (SEQ ID NO: 65) 33156LQELKYSFQTNDRLCFVMEFAIGGDLYYHLNRE  33254 AKT (21 amino acid motif) (SEQID NO: 66) 30836 VVIEGWLHKKGEHIRNWRPRF  30898 AKT (26 amino acid motif)(SEQ ID NO: 67) 33276 FSEPRARFYGSEIVLALGYLHANSIV  33353 DAF-4 (139 aminoacid motif) (SEQ ID NO: 20)   380EYWIVTEFHERLSLYELLKNNVISITSANRIIMSMIDGLQFLHDDRPYFFGHPKKPIIHRDIKSKNILVKSDMTTCIADFGLARIYSYDIEQSDLLGQVGTKRYMSPEMLBGATEFTPTAFKAMDVYSMGLV MWEVISR  518 DAF-4 (61amino acid motif) (SEQ ID NO: 21)   537IGFDPTIGRMRNYVVSKKERPQWRDEHKHEYMSLLKKVTEEMWD PEACARITAGCAFARV  597 DAF-4(20 amino acid motif) (SEQ ID NO: 22)   305 PITDFQLISKGRFGKVFKAQ  324DAF-8 (163 amino acid motif) (SEQ ID NO: 23)   382TDSETRSRFSLGWYNNPNRSPQTAEVRGLIGKGVRFYLLAGEVYVENLCNIPVFVQSIGANMKNGFQLNTVSKLPPTGTMKVFDMRLFSKQLRTAAEKTYQDVYCLSRMCTVRVSFCKGWGEHYRRSTVLRSPVWFQAHLNNPMHWVDSVLTCMGAPPRICSS  544 DAF-8 (44 amino acid motif) (SEQID NO: 24)    91 RAFRFPVIRYESQVKSILTCRI-IAENSHSRNVCLNPYHYRWVE LP  134DAF-8 (38 amino acid motif) (SEQ ID NO: 25)   341VEYEESPSWLKLIYYEEGTMIGEKADVEGHIICLIDGFT  378 DAF-14 (39 amino acidmotif) (SEQ ID NO: 68)  9709 IRVSFCKGFGETYSRLKVVNLPCWIEIILHEPADEYDTV9825 DAF-14 (45 amino acid motif) (SEQ ID NO: 69)  9409SRNSKSSQIRNTVGAGIQLAYENGELWLTVLTDQIVFVQCPFLN Q  9543 DAF-14 (29 aminoacid motif) (SEQ ID NO: 70)  9160 NEMLDPEPKYPKEEKPWCTIFYYELTVRV  9246DAF-14 (29 amino acid motif) (SEQ ID NO: 71)  9307QLGKAFEAKVPTITIDGATGASDECRMSL  9393 DAF-12 (105 amino acid motif) (SEQID NO: 72)   103 SPDDGLLDSSEESRRRQKTCRVCGDHATGYNFNVITCESCKAFFRRNALRPKEFKCPYSEDCELNSVSRRFCQKCRLRKCFTVGMKKE WILNEEQLRRRKNSRLN  207DAF-12 (89 amino acid motif) (SEQ ID NO: 73)   109LDSSEESRRRQKTCRVCGDHATGYNFNVITCESCKAFFRRNALRPKEFKCPYSEDCEINSVSRRFCQKCRLRKCFTVGMKKEWILNFE Q  197 DAF-12 (73 aminoacid motif) (SEQ ID NO: 74)   551DIMMMDVTMRRFVKVAKGVPAFREVSQEGKFSLLKGGMIEMLTVRGVTRYDASTNSFKTPTIKGQNVSVNVD  623 DAF-11 (112 amino acid motif) (SEQ IDNO: 75)   708 SGSLVDLMIKNLTAYTQGLNETVKNRTAELEKEQEKGDQLLMIELLPKSVANDLKNGIAVDPKVYENATILYSDIVGFTSLC SQSQPMEVVTLLSGMYQRFDLIISQQGGYKV  819 DAF-11 (107 amino acid motif) (SEQ IDNO: 76)   825 METIGDAYCVAAGLPVVMERDHVKSICMIALLQRDCLHHFEIPHRPGTFLNCRWGFNSGPVFAGVIGQKAPRYACFGEAVILASKMES SGVEDRIQMTLASQQLLEE  931DAE-11 (43 amino acid motif) (SEQ ID NO: 77)   520DILKGLEYIHASAIDFHGINLTLHNCMLDSIIWIVKLSGFGVNR L  562 DAE-11 (15 aminoacid motif) (SEQ ID NO: 78)   618 DMYSFGVILHEIILK  632 DAF-7 (60 aminoacid motif) (SEQ ID NO: 26)   290NLAETGHSKIMRAAHKVSNPEIGYCCHPTEYDYIKLIYVNRDGR VSIANVNGMIAKKCGC  349 DAF-7(20 amino acid motif) (SEQ ID NO: 27)   265 DWIVAPPRYNAYMCRGDCHY  284DAF-7 (43 amino acid motif) (SEQ ID NO: 28)   240VCNAEAQSKGCCLYDLEIEFEKIGWDWIVAPPRYNAYMCRGDC 282 DAF-7 (70 amino acidmotif) (SEQ ID NO: 29)   281DCHYNAHLIFNLAETGHSKIMRAALIKVSNPEIGYCCHPTEYDYIKLIYVNRDGRVSIANVN GMIARKCGCS  350 DAF-7 (35 amino acid motif) (SEQ IDNO: 30)   250 CCLYDLEIEFEKIGWDWIVAPPRYNAYMCRGDCHY  284 DAF-7 (13 aminoacid motif) (SEQ ID NO: 51) GWDWIVAPPRYNA DAF-7 (9 amino acid motif)(SEQ ID NO: 364) GWDXXIAPK

DAF-7 (9 amino acid motif) (SEQ ID NO:304). GWDXXIAPK

In one particular example, mammalian DAF-7 may be identified using thesub-domain amino acids 314–323. Exemplary degenerate oligonucleotidesdesigned to PCR amplify this domain or hybridize (for example, asdescribed in Burglin et al., (Nature 341:239–243, 1989) are as follows:

aa 263 oligo: GGNTGGGAYTRINRTNRTNGCNCC (23-met, 16,000-fold degeneracy)(SEQ ID NO: 31) aa 314 oligo: TGYTGYNNNCCNACNGAR (18-met, 8000-folddegeneracy). (SEQ ID NO: 32)

The DNA sequence between the oligonucleotide probes is determined, andthose sequences having the highest degree of homology are selected. Onceisolated, these sequences are then tested in a C. elegans daf-7 mutantor mouse model as described above for the ability to functionallycomplement the mutation or ameliorate the glucose intolerance phenotype.

To date, the closest homologues of C. elegans appear to be members ofthe vertebrate GDF-8 and GDF-11 gene family, with a representativehomologue shown in FIGS. 47A and 47B. These human proteins, whosecomposition and function in muscle size determination have beendescribed (McPherron A C, Lee S J, Proc Nati Acad Sci U.S.A. 1997 Nov.11; 94(23):12457–61), may also function in metabolic control inconjunction with insulin. Altemtaively, there may be more than one DAF-7orthologue, or a closer relative to DAF-7 in mammalian databases thatsubserves the metabolic role, whereas GDF-8,11 serve related roles inmuscle control. The DAF-7 gene does not appear in worm EST databases,most likely because it is expressed in a single neuron, a very lowexpression level. Even though the mammalian EST databases are about 10fold larger than the C. elegans EST base, if human DAF-7 is expressed ina small set of neurons, it is not surprising that it has not yet beenseen in the EST database. Nonetheless, human DAF-7 may be instantlyrecognized using the motif, GWDXXIAPK (SEQ ID NO:304) as a means tosearch updated sequence databases or by standard techniques as describedherein.

Other Embodiments

In other embodiments, the invention includes any protein which possessesthe requisite level of amino acid sequence identity (as defined herein)to DAF-2, DAF-3, or a DAF-16 sequence; such homologs include othersubstantially pure naturally-occurring mammalian DAF polypeptides (forexample, human DAF polypeptides) as well as allelic variants; naturalmutants; induced mutants; proteins encoded by DNA that hybridizes to theDAF DNA sequence or degenerate conserved domains of DAF proteins (e.g.,those described herein) under high stringency conditions; and proteinsspecifically bound by antisera directed to a DAF-2, DAF-3, or DAF-16polypeptide.

The invention further includes analogs of any naturally-occurring DAF-2,DAF-3, or DAF-16 polypeptides. Analogs can differ from thenaturally-occurring protein by amino acid sequence differences which donot destroy function, by post-translational modifications, or by both.Modifications include in vivo and in vitro chemical derivatization ofpolypeptides, e.g., acetylation, carboxylation, phosphorylation, orglycosylation; such modifications may occur during polypeptide synthesisor processing or following treatment with isolated modifying enzymes.Analogs can also differ from the naturally-occurring DAF polypeptide byalterations in primary sequence. These include genetic variants, bothnatural and induced (for example, resulting from random mutagenesis byirradiation or exposure to ethanemethylsulfate or by site-specificmutagenesis as described in Sambrook, Fritsch and Maniatis, MolecularCloning: A Laboratory Manual (2d ed.), CSH Press, 1989, or Ausubel etal., supra). Also included are cyclized peptides, molecules, and analogswhich contain residues other than L-amino acids, e.g., D-amino acids ornon-naturally occurring or synthetic amino acids, e.g., β or γ aminoacids.

In addition to full-length polypeptides, the invention also includesDAF-2, DAF-3, and DAF-16 polypeptide fragments. As used herein, the term“fragment,” means at least 20 contiguous amino acids, preferably atleast 30 contiguous amino acids, more preferably at least 50 contiguousamino acids, and most preferably at least 60 to 80 or more contiguousamino acids. Fragments of such DAF polypeptides can be generated bymethods known to those skilled in the art or may result from normalprotein processing (e.g., removal of amino acids from the nascentpolypeptide that are not required for biological activity or removal ofamino acids by alternative mRNA splicing or alternative proteinprocessing events).

For certain purposes, all or a portion of the DAF-2, DAF-3, or DAF-16polypeptide sequence may be fused to another protein (for example, byrecombinant means). In one example, the DAF polypeptide may be fused tothe green fluorescent protein, GFP (Chalfie et al., Science 263:802–805,1994). Such a fusion protein is useful, for example, for monitoring theexpression level of the DAF polypeptide in vivo (for example, byfluorescence microscopy) following treatment with candidate or known DAFagonists or antagonists.

The methods of the invention may be used to diagnose or treat anycondition related to glucose intolerance or obesity in any mammal, forexample, humans, domestic pets, or livestock. Where a non-human mammalis diagnosed or treated, the DAF polypeptide, nucleic acid, or antibodyemployed is preferably specific for that species.

All publications and patent applications mentioned in this specificationare herein incorporated by reference to the same extent as if eachindependent publication or patent application was specifically andindividually indicated to be incorporated by reference.

Other embodiments are within the following claims.

1. A method of diagnosing an impaired glucose tolerance condition,obesity, or a propensity thereto in a mammal, said method comprisinganalyzing the level of mammalian PTEN expression or activity in a sampleisolated from said mammal, whereby an increase in said level of PTENexpression or activity relative to a control sample is an indication ofan impaired glucose tolerance condition, obesity, or a propensitythereto.
 2. The method of claim 1, wherein said level of PTEN expressionor activity is analyzed by measuring PTEN lipid phosphatase activity. 3.The method of claim 1, wherein the said mammal is a human.